Well, if you look at what they're doing in the courts they're not trying anything so broad (if for no other reason than that they'd fail; do you claim they'd get any traction against Books-A-Million) and all their reported efforts looked OK to me (the parody site is a wobbler, but it sounds like it was settled amicably enough).

Focus on the "confusingly similar"; if you're for example doing sometime social and name yourself <one or two syllable whatever>book, aren't you trying to gain something by being very similar to their mark?