Are books made into movies always successful?

Tonight I'm going to see the Time Traveler's Wife. I read the book a couple weeks ago in about two days flat. I really liked the book - everything but the ending. It just didn't cut it for me. But when I read that the director altered the ending to the movie slightly, I was for once, excited.

My previous encounter with the book-made-into-a-movie scenario was My Sister's Keeper. I read the book a few years back and it was great. Super sad and definately a tear-jerker but the entire book (including the end) was one cohesive and amazing message. So once I heard that a movie was made, I was beyond pysched about seeing it....until...I heard they changed the ending. I went a step ahead and read a spoiler and sure enough, they altered the entire meaning. I was so pissed, I refused to see the movie and I still haven't seen it.

So, long story short, let's hope this movie rocks tonight. :)