Gosick starts out as semi-episodic mystery anime, with each case taking 2-3 episodes. This goes on for the majority of the show.
The cases often dealt with the occult or at least he illusion of the occult, and were very interesting. Victorique would solve the cases after Kujo, the typical shounen protagonist, would somehow stumble upon clues that she needed. A fairly simple formula, but the reason you will like this is because of the nature of the cases.
However the last 6 or 7 episodes are no longer about solving captivating cases of the occult. Instead the show shifts focus to the rather forced romance of Victorique and Kujo, and they go through some dramatic things to make their romance seem tragic. I was really disapointed when I realized the show was done being a mystery and just going to go full cliche tragic romance on me. This show didn't know what it wanted to be.
Victorique remains an interesting character for most of the show. She's your typical tsundere but she's also a Grey Wolf, a Golden Fairy, and a Charming Monster.
Kujo is a terrible character. He get's really really annoying whenever Victorique is in danger.
Grevil does his job well as a hybrid comic-relief/serious character. Just look at his hair, it speaks for itself.
This show gets a pass from me for its captivating cases of the occult, and for the well done air of mystery around the Grey Wolves and what was the groundwork for the main plot. However I have to dock it down for its extremely rushed/unneeded cheesy tragic romance for the last 1/4th of the show. And also for its rushed conclusion of the main plot.