While I see what you're saying at the end, I care much less than you seem to about whether the book I read tonight will be as good as the book I read last night. But I grab a lot of books from the library, based mostly on what grabs me at the moment; while I want every book I grab to be really good, there are various shades of less-awesome that inevitably happen.I finished reading Cameron Reed's The Fortunate Fall. That was a book so good that I was left struggling what to read next. It had so many layers to it, and one heck of an ending.
I eventually decided on Philip K. Dick's Flow My Tears, the Policeman Said for my next read. You have to follow greatness up with either more greatness, or schlock. Anything in-between just won't do.
That said, there have been times when a book probably did seem worse than it was to me, because the previous book had been so excellent.