One of the most common questions I get it might be the most common is "Who would the author cast as Lucas in a movie?"  Or sometimes it's the same question about Virgil Flowers. More rarely, people ask about the secondary characters: Weather, Rose Marie, Del, and so on.
Now, the author has his own ideas about it, as do I.  A typical answer for the Lucas question is that the author's mental image of Lucas looks a lot like Pat Riley, current coach of the Miami Heat basketball team, as he was twenty years or so ago. He had the face, the build, and importantly the suits. But Riley isn't an actor, and he's aged twenty years since his prime "Looks like Lucas" days, so it's not going to happen.
This type of intellectual exercise is fine. Sure, it might not be possible to cast a young Clint Eastwood  anymore the young Clint Eastwood grew into the modern-day Clint Eastwood but the casting game can be fun, and is usually harmless. 
But then there are people who write in making demands. They'll say that some actor must be cast as Virgil,  and the author needs to do that ASAP. Or they'll complain that Mark Harmon should never have been cast as Lucas,  and the author should be ashamed. At this point it's not fun. And so I have to explain how movie rights work with respect to authors. 
There have been, to date, two Prey movies, both for TV: Mind Prey, with Eriq LaSalle as Lucas, and Certain Prey with Mark Harmon as Lucas.  Neither one was cast by the author, or featured actors recommended by the author, or had scripts approved by the author, or anything. He was not asked for consent, because it was not required. The author did not have the rights.
And that is the simple truth of it: when an author sells the movie rights for a book, he or she loses any and all control they might have.  They don't have any say over the screenwriting. They don't have any say over the casting. They don't have any say over who will direct, or where it will be shot, or how faithful the adaptation will be to the book, or how much money will be spent. Once the author signs the contract, the rights are gone. 
And sometimes it's more complicated, and involves what I call the James Bond clause.  The character of James Bond is owned by one particular company, so nobody else can make a James Bond movie.  Oh, sure, other companies could make a James Bond -like movie that happens every so often but they can't use the character, because the rights to the character are already owned.
For the Prey series, the author did not individually sell the rights to Mind Prey and then later Certain Prey. No. He sold the rights for Rules of Prey just that one, since there were no others yet way back in 1990, but those rights included a James Bond clause. The rights included exclusive license for the Lucas Davenport character in all books as yet written, and all yet to be written.
And every original character that appears in that book.
And every original character that appears in any book Lucas is in. 
And every book that those original characters appear in.
And it keeps chaining out like that, potentially forever. So for the Prey series, he sold the rights back in 1990 for one book, but that was enough to include... everything.
Lucas is in every Prey book, so the rights to every
book are included in the original contract. So, yes, the rights to Field of
Prey, which isn't even out yet, were sold way back in 1990.
Kidd appears in Eyes of Prey, and so the rights to the Kidd novels are included.
Virgil Flowers is introduced in the seventeenth Prey novel, and so all of his books are included in the contract as well.
And while people may say that it's not fair to the authors, or that the authors shouldn't sell out like this, the truth is that this is how it's done all the time.  This is how Hollywood works. If you're an author, you do not get to pick and choose anything about a potential production. You sell the rights to a company you probably don't know anything about and hope that they get it right.  Sometimes they do.  Sometimes they don't.  But you won't know until long after you've sold those rights.
If you're an author, there really is no such thing as waiting for the right company to come along. You're always in the dark about how they'll handle it. You either never sell the rights to anyone, ever, or you sell them blindly and hope for the best.  And that's the end of it.
Oh, And By The Way...
If anyone wants to buy the rights to the Prey series, they're currently held by Jaffe / Braunstein Films. I don't know if they're available for purchase, but I don't know that they're not. And if they are, I have no idea what the asking price is. So... yeah.
- It's also one of the most popular topics on various message boards. Not just for John Sandford, but for any author. And, as happens in internet message boards, it's a topic that incites very strong emotions. Answering, "Well, the author really has no say" just doesn't play to that very well.
- Although, honestly, I probably think about it more than he does. Both in the sense of "How could this be faithfully adapted?"  and "Is it even possible?"  I rarely think about individual casting ideas because the current crop of actors changes so frequently. 
- Young Clint Eastwood is a fairly common choice when people suggest an actor to play Lucas. I don't know if anyone has contact information for Young Clint Eastwood anymore. At least, not that anyone can use. 
- Although I got a few death threats after the Mind Prey TV movie. 
- The current favorite fan suggestion for Virgil is Matthew McConaughey. The author and I agree that Owen Wilson would probably be a better fit. 
- Mark Harmon is, physically, quite close to Lucas in height, build, style, and a bunch of other things. If you thought that he was physically way, way off, then I honestly don't know what you expect. This isn't a Tom Cruise / Jack Reacher situation.
- Which is honestly the point of all of this. Rather than answering all the questions individually while simultaneously increasing the dosage on my blood pressure medication, I can just direct people to this rant.
- Both were by the same production company, albeit for different networks, and both were shot in Toronto. 
- This is a blanket generality and is not 100% true. Sometimes authors do get a modicum of control over an adaptation of their work. When that happens, they usually take a huge cut in pay. When the Rules of Prey movie rights contract was signed in 1990, the author didn't know it would even be a series, let alone a long-running one. So there didn't seem to be much risk with signing the rights away. 
- There's usually a Sunset Clause in the contract: if the production company doesn't make a movie within a certain time limit, the rights revert back to the original creator. The Rules of Prey movie contract does not have a Sunset Clause. He's never getting the rights back. Ever. 
- At least, that's what I call it. There's probably a technical name for it, but I have no idea what it is.
- There was one exception, and it went to court. While one production company had the copyright for all of the movies, one of them Thunderball had a co-copyright, or co-ownership, or something like that. In the 1980s the co-copyright owner remade it as Never Say Never Again starring Sean Connery as James Bond. It's considered the illegitimate child of the Bond franchise, as it wasn't made by the official Bond rights holders. A strange situation. And, as I said, it went to court. Click here to read more.
- Well, any John Sandford book that Lucas appears in. Lucas appears in a few Chuck Logan books (although he's not named) as well as works by a few other authors. Those don't count.
- This is one way to look at it. Another way is that this is the only way they do it. Since it's the only way to do it, it happens all the time. And it happens all the time because it's the only way to do it. QED.
- In the age of the internet you can usually do research a lot faster. The company that bought the movie rights to Rules of Prey was called Film & Television, Ltd. But back in 1990, there was no quick or convenient way to research them. We know that it was sort of linked to ICM, the agency that represents John Sandford, but that was it. We later found out that it was Dino DeLaurentiis' company. But by then it was too late. 
- Chuck Palahniuk said that the adaptation of Fight Club was much closer to what he wanted his novel to be than what the novel actually was.
- For people upset that Eriq LaSalle got cast as Lucas, remember that Leonard Block's Burglar series of novels was turned into a comic movie starring Whoopi Goldberg. Now, whatever your opinion of Whoopi, you've got to admit she doesn't look much like a middle-aged white book dealer.
- The general advice is to take as much money as you can get, and never ever view the finished product. Anything less will just lead to heartbreak.
- For some strange reason, people don't like "We just don't know" as an answer. Why is this? 
- I feel that the Prey series could be done, but not as a movie. Do it as a cable TV series, on HBO or some similar channel, with three books per year. Thirteen episodes in a season, three episodes per book, with stand-alone single episodes between the books to fill in gaps. Sometime in the third season there'd be an episode covering Del and the Pinking Shears Incident. 
- This is a trickier question. Oh, there's no doubt that you could adapt it... but could you do it in a way that captured the depth of the characters? In the early books, Lucas is heavily involved in gaming.  In the first movie, that part of his personality is hinted at when you see him working on a computer game at home. In the second movie... there's not even that small hint. You could do it over time in a regular series, but for a one-off movie the main character is going to be another generic thriller hero with one or two token quirks to make him or her stand out.
- And now that I've disclaimed myself to perdition and back, I think John Barrowman would be a striking Lucas.
- Imagine that you build a time machine, and you use it to go back in time and procure Young Clint Eastwood for a movie. Can you imagine what the legalese on that contract would look like? I mean, forget the temporal paradoxes that could destroy the integrity of the space-time continuum. When you bring in Hollywood lawyers, you're really playing with fire.
- This was in the Bad Old Days of the early internet. There were a lot of complaints about the TV movie via snail mail, but the novelty of instant-and-anonymous electronic-mail enabled quick and easy death threats. I imagine the senders all subscribe to Internet Tough Guy quarterly. 
- I sold him on Owen Wilson. The only downside is that they'd probably get Ben Stiller to play Del, and that would be terrible. 
- The second one at least had footage of the Twin Cities. As for the first one... I think they mentioned Minneapolis a couple of times, but that's about it.
- At the time, Dino DeLaurentiis was known for making terrible low-budget movies (and occasional terrible high-budget ones). Sure, there were a few decent movies in there, but you'd expect that from random chance.
- We just don't know. 
- And of course you would never ever actually see the critical event. You'd see Del talking to a woman holding pinking shears, and then jump-cut to Lucas on the phone, saying, "Wait, she did what?" And you'd never ever find out more.
- Another common misconception is that Lucas worked on video games. He didn't. He worked on old-school tabletop role-playing games, like Dungeons & Dragons or GURPS. The one he's working on in Shadow Prey sounds like a dystopian cyberpunk setting similar to Shadowrun. The author himself doesn't know much about the gaming scene that's my thing or he'd know there's no money to be made there. 
- ITG Quarterly.
- Or possibly awesome.
- "What are birds?"
- At least, not by individuals. By studios, sure.