too much technical stuff that doesn't clearly connect to the plot. The bowyer bits in KJ Parker? really interesting. The plain descriptions in Patrick O'Brien? skim city. John Updike and his overblown modifiers. Most of John Irving, because his deaths and dismemberments as plot devices bore me. Books where the main characters are whiney white men who think the world owes them (I'm looking at YOU, Holden Caulfield)...

OTOH, naval battles? fab.

Oh, and anything that is implausible and you can tell the author doesn't realize it.