Larry Niven's books are all for the most part movie ready. They have big expansive ideas and visuals and plots that are generally fast pace and linear. If there is a slight to his overall performance as a writer its that he's not as much into characters as into ideas. But that can be fairly easy fix in screen writing and the right actor or actress can really breath life into a character.
Dream Park would make an interesting film because it straddles so many genres so deftly. It's one part mystery, one part science fiction, one part fantasy adventure, and one part meet the geeks. In the near future there is Dream Park which is like Disney plus. It doesn't quite have Star Trek level holodecks (thank God, cause that would be the end of the world), but it does have very realistic holograms that make the rides true experiences. One part of the park is dedicated to the games which are basically life sized versions of D&D with holograms. There is a theft and a death and trail leads back to where the gamers are. The park doesn't want to stop the game because they make millions off of them so they infiltrate the head of security into the game so he can find the thief. Of course, he sticks out like a sore thumb among the dedicated gamers, but soon he gets into the adventure.
One thing that makes this such a fun novel and an even better movie is the adventure they take. It's not some boring old dungeon crawl. Rather, they use cargo cult (a real thing look it up) mythology. You have got to love any mythology where coca cola is the magic potion of choice. I also like how the hero's journey here should mirror the film audience in that we all know it isn't real but we become emotionally invested anyway. That becomes very true later on when "dead" players get back some of their hoarded gamer points by coming back as zombies. Even though it's all play there is something very creepy about "killing" your own teammate.
All in all, it would be a fantastic exciting film. I think it would really resonate in this era of World Of Warcraft and PS3s. Anyway, that's my idea. What book would you like made into a film?