I enjoyed the Ready Player One movie a lot. It was fun, visually appealing, and kept up a good pace. Books always lose nuances when translated to film, and I think that they did a pretty good job in tweaking the plot to make it fit into one film. The dialogue and character building was pretty sloppy and cliche, and to me was the weakest part of the movie. But, it was still nice to see the dozens of references and cameos from the history of geekdom.
I think Ender's Game was a decent attempt at converting a book into a movie. They rushed a few things, and again the dialogue was simplified, but it managed to get the core message of the book across.
On a bit of a different tack, Leonard Bernstein made an operetta version of Candide that is hilarious and really well done. There are a few different versions of it, but the 2005 Live on Broadway version features Kristin Chenoweth as Cunegonde and Patti LuPone as The Old Lady. There's an okay copy on YouTube, but I'm sure there's a better version to be found in other less reputable corners of the internet.
There are actually quite a bit of shows and movies on the way that are based on Fantasy and Sci Fi novels, probably thanks to Game of Thrones' success. Amazon and Sony are putting The Wheel of Time into production, TNT is drafting a pilot for The Broken Earth series, BBC is in production with Good Omens, Netflix is working on The Witcher, Amazon is working on a five-season series based on Lord of the Rings, and The Kingkiller Chronicle is getting a prequel TV series (with Rothfuss working with Lin Manuel Miranda, so that's pretty exciting) as well as film versions of the books through Lionsgate. The BBC is also working on a new series for His Dark Materials, as well as a procedural crime drama based on Terry Pratchett's Ankh-Morpork City Watch. Pratchett's production company, Narrativia, teamed up with The Jim Henson Company to produce the first of his young adult novels, The Wee Free Men, into a movie. So there's a lot of exciting potential for good translations of these amazing books onto film.
I feel like the advent of Netflix and Amazon as production companies has really breathed new life into book-to-film adaptations. Being able to create them as episodic shows allows them to keep way more of the source material intact, instead of having to carve away parts of the story to fit it into a single movie.
(Photo: David Tennant and Michael Sheen in Good Omens)