Many times it is only possible to know that post hoc. There are several books I've read that, in the moment of completing them, stand as the best I'd read in the past few years. Others I finished and figured I'd never think of them past the current month.

But books and their impact upon you can be surprising sometimes. There are some books I think about often, and that I would say have even influenced me greatly, that I wouldn't have guessed would have that impact when I read them. And others that I figured would remain "book of the decade" that barely made it to the two-year mark before being surpassed by something else.