To be brutally honest, I felt like the movie was a very poor adaptation of a fairly poorly written book from an overall unenjoyable trilogy. I trudged through the second and third books because the premise was very interesting. I don't think Jeff can deliver a story that one, at least I, can be fully satisfied by.
I hesitate to tell people to avoid the books altogether because the premise is interesting enough and the books arnt outright awful but I really cant recommend them to anyone.
What am I missing that many other people seem to be connecting with?
I'll offer a third opinion here, which is that the book is literally not possible to recreate accurately in film using current technology.
The challenge is that in Annihilation VanderMeer is very interested in the idea of a thing which challenges on a basic level the very way humans sense things. He heavily exploits the format of writing to accomplish this. The descriptions he includes are frequently impossible, contradictory, or non-sensical. Additionally, these descriptions are simultaneously specific and vague - and this tension between specificity and vagueness is itself a property of the things he describes in addition to the narrative technique. This seems very intentional to me - but in any case it relies heavily on a subjective interpretation formed in the reader's mind's eye. It is possible to imagine a thing with these kinds of phantasmagoric, perhaps dreamlike properties, but the film medium, as we know it, doesn't allow for that kind of flexibility - the moment an image is crystallized on film, it becomes a fixed, static thing for all viewers.
So in translating this to film format I think Garland really had to have his own personal take on the ideas in the book. Personally I thought it was a good (but flawed) movie with certain superficial similarities to the book in terms of plot. There were many directions a film based on this book could go; as has been shown by many book-to-film adaptations, a novel can be more tightly packed with information than a 2-hour movie. I think Garland chose some interesting facets of the book to focus on while doing something unique.
To answer your question - "What am I missing that many other people seem to be connecting with?". As someone who thought the first book was good (but perhaps not great), here is what I felt would be compelling to most readers:
1) The book was paced and structured sort of in a Dan Brown esque way. Events move quickly from scene to scene and every chapter leaves you with a lot of unanswered questions with potentially intriguing resolutions (e.g. What is going on in Area X? What is the creature/pit/lighthouse? What information are the protagonists hiding from one another? What happened to the other expeditions? What is the literal writing on the wall?). In short, it is a mystery, which is a good hook for many readers.
2) The book leaves a lot for the reader to fill in for his or her self. You get that impression that the characters in the book are also experiencing something similar themselves in their world. This is an interesting thought.
3) The book does some unconventional things. The main characters are not identified by name, rather their profession. The main characters are all female and they are all scientists. Etc.
One of the most disappointing things to me about the movie was how it looked conventional near the end. The action- or maybe inaction- sequence was certainly different and deliberating- but the heart of the asteroid was boringly Giger, and the CGI was not great.
I hesitate to tell people to avoid the books altogether because the premise is interesting enough and the books arnt outright awful but I really cant recommend them to anyone.
What am I missing that many other people seem to be connecting with?