How forgiving are you when you come across a continuity error in a published book/series of books? I'm not talking about changing eye/hair color, a forgotten knife suddenly in the hero's hands. Those things are annoying, yes, but I'm talking about plotty things. Like X doesn't know who did harmful Y but intends to find out, then in book 2, suddenly it is X who did Y to serve his own purposes. o.O (And no, there was no explanation. It is apparent that the author forgot what she had said in book 1 because a) X doing so makes no sense despite the author's reasoning, b) there is NO explanation, c) harmful Y was too full of plotty goodness as it was presented in bk 1. X doing Y takes out alllllllll of the tension.)
How about when an author, again in bk 2, seemingly decides they no longer like the way they set up a certain aspect in book 1 and continues to repeat the "new" fact over and over again, either trying to convince you or themselves that that's really the way things happened in the first volume? Yeah, annoys me, too.
As an aspiring author, I've written my share of slips, but why doesn't someone catch these things? Beta readers, an agent, an editor, a copy editor?
Are these mistakes enough to keep you from reading an author, or do you forgive them as well?