For me it’s the Night School series. I’ve loved those books and they’d be easy to make into a film! There’s already a fan made trailer for them on youtube and I think the author of the books already got an offer to make them into movies but that was a few years ago. I don’t know why they didn’t make a movie yet
The first books that comes to mind is The Stormlight Archive series. They would probably work better as a tv series though. A film could be awesome, but there’s so much detail that would get lost.
I’d really like to see The Lunar Chronicles made into movies or a movie. I really wanted The Selection series to get a movie and now it is, just after this whole pandemic.
I also want “How to train your dragon” as a movie, but a version that stays more true to the books. I mean, the books were hilarious The movies that exist now are kind of boring in comparison hehe.