The last two episodes of Gosick (which I just recently got around to watching) are so much of a change that I got whiplash, and are among the fastest I've seen an anime series descend into more or less incoherence. It's as if the writer and director woke up after episode 22 and realized that they still had two thirds of the story to cover and only two episodes left.

(There are spoilers here.)

As you'd expect the result was less a story than an extended summary of a story. There were abrupt and unexplained lurches in what was going on (at the end of episode 22 Kazuya was being held by the Ministry to get Victorique's cooperation; at the start of episode 23 he is in military training in Japan). Major story events casually took place offscreen (eg Cordelia freeing Victorique from captivity). What we did see was often drastically out of tune with how Gosick was before. Characters did abrupt changes in characterization that made it hard to care about them. Completely inexplicable yet very convenient things kind of happened. And amid all of this the show spent times on scenes that seemed to do nothing (eg Kazuya's hallucinations, if they were hallucinations).

(I also feel disturbed by what the last two episodes seem to imply about the show's world; they casually present a situation where it seems that Germany may have won that world's version of World War II. Japan has a nice real-world habit of considering WW II to be this not a big deal that other people make too much of a fuss about as it is, so seeing anime downplay it makes me twitch.)

Apart from the last two episodes, Gosick was a decent show. Unfortunately episode 22 doesn't end on a good stopping point so you can't really pretend that the last two episodes never happened.