The joy of movie adaptations

Sometimes I wonder why Hollywood even bothers to adapt books into movies.  They must make a profit off of it, or they wouldn't keep doing it, but it seems to generate ungodly amounts of ill will among the target audience. 

Anyone who has read a decent-length novel knows that fitting everything from the book into a visual format would take the kind of time that usually requires a miniseries or a full length series (with multiple seasons).  As a result, they should know that if the adaptation is only going to get 2 hours of screen time, a majority of the details of the book are going to be missing, yet most readers of the book take these missing details very personally and throw a huge fit every time and seem incapable of judging the film on its own merits, coherence, and success.  Their ardent and vocal disappointment at not seeing the entire contents of the book transferred comprehensively to the screen is sort of understandable but also a little immature and maybe kind of silly. 

Understandable because everybody has a favorite scene they wanted to see and because the things that make the book successful are usually related to internal access and extended character development impossible to do on-screen in a couple hours.

Silly because, well, if you set your expectations way too high, it's your own fault when reality doesn't live up to them.  I generally find it more pleasant to have very low expectations and be pleasantly surprised most of the time.

How have you fared with movie adaptations of  books you haven't read and those you have?  Any winners?