The book is one of my favorites of all time. I can't recall having a more enjoyable experience while reading a book. I kept stopping to look up various references (like the Tomb of Horrors module), then my mind exploding when I saw the module cover & realized "Hey! I remember playing that as a kid!". The book was REALLY speaking to my childhood memories. Ultraman! R2-DJ! Meccagodzilla! I even learned about things I had no clue about, such as the 1970's Japanese Spider-Man's battle robot Leopardon. Such an enjoyable read.
The movie changed quite a lot from the book, but that's what I expected. The mass movie going public does not know Leopardon & Ultraman, but they do know Iron Giant. That's an acceptable trade off, and there were many examples like that. Many changes for convenience sake, but tons of easter eggs too. There was no way they were going to fit everything into the movie, nor would they be able to get all those pop culture licences. I'm really looking forward to watching it again on bluray, so I can pause it & spot things I missed on the first viewing. I can't think of any other movie that has this many "blink-and-you'll-miss" easter eggs.
The thing I enjoyed the most was that Sorrento's avatar was based an evil Alex Ross version of Superman. That completely blew my mind. I've always dreamed of a CGI adaptation of Kingdom Come, so seeing that Superman version on the screen sure gave me a thrill 
