Now, this is not always the case. There are books that, like the Pass of Caradhras, slowly mire me down until I reach a point where I can go no further. There are also some books for which I am so ravenous, such as when The Deathly Hallows first arrived, that I can consume them at a breakneck pace from start to finish, sometimes staying up throughout the night to finish almost 800 pages in a single sitting. Fortunately, these exceptions prove the rule.
Generally, I find that it takes me time to settle into a book as I am learning the characters and world that is established. My pace slows a bit as they begin to encounter their difficulties, particularly since I have to keep forcing myself to the book to face their miseries. However, as the story reaches its climax, I almost trip over myself to find out how everything comes together. Thus, by the end, I often feel like the story concluded entirely too fast--this is particularly true for stories that end of cliffhangers or just have a short denouement.
It's at that point that I sometimes need to take a breather before embarking on another imaginative journey.