So, you read a really good book, And I mean REALLY good. And then you read another. And another. And you're on top of the world. You're all, "WOOOOOOOOOOO! BOOKSBOOKSBOOKS!"
And then you read another book, and while it's by no means a bad book, it is definitely doesn't match the other three's Level of Awesome. Now you're finding yourself kind of blah about it, though it's not the book's fault, really. It's you. You're just kinda of blah towards reading in general, at the moment.
I call it The Good Book Hangover.
I currently have it.
Don't like it. At all.