Gosick

The last arc is quite different in the anime and LN.
In the LN, there is supernatural involved (a bit, but important), and situation for victorique and her mother is far harsher (well, it was harsher the whole time, the anime version basically removed all part that could shock viewers). The main things (who dies, who don't, who ends up with who) are mostly the same. One exception is that Victorique's father doesn't die, and was never in danger of dying. the scene of Victorique's mother fighting doesn't exist. It doesn't make sense anyway, as she is a dancer, not a fighter; and victorique's father is a politician and a noble, not a fighter either.
Instead, her mother indeed take place of victorique as well (but it's inside a prison, told you victorique's position was on a whole different level of "harsh" compared to anime), and as soon as she's discovered, she's executed with one of the Brian roscoe by guards piercing her with their spear without them trying to resist.
The second brian roscoe doesn't fall from a cliff. He does indeed die on the boat, but for a whole different (and far more logical reason).

Supernatural power cannot leave the old continent. Brian Roscoe is a pure blooded Seirun tribe, and as such, is a supernatural tribe. He dies after weakening a lot on the boat, just like any other supernatural being who tried to escape the old continent because of war. Victorique however survives because she's a mixed blood. Still, her hair completely lose the golden color (that part wasn't explained in the anime), and is in coma state when arriving to japan. There, she's sold by the boat crew to a japanese procurer, who intends to do of victorique a prostitute. However, when he undress her to give her a bath as she's still unconscious, he realize this won't work for a good reason and leave her free. That 'good reason" is due to a scene that doesn't happen in the anime either. Awesome scene, which is replaced by that scene with victorique looking at Kazuya by the window and crying in the anime. Well, both scene were good, in a different way. In the LN, Victorique is awesome in that specific scene ( she tatoo herself) from start to finish (when his brother comes to bring her to prison); in the anime, the emotional impact here is strong, but victorique is her usual crying self, so her development as a character is lost.
The head of the academy faction (who fled in the anime) never fled since he had no reason to (the katamibako was never delivered to the occult faction) for example, so those weird guys screaming "monstre charmant" everywhere wearing a rabbit head never appear in the LN, that's an invention (and a poor one imo) of the Anime staff, so differences exists in previous arcs as well, and those differences together are heavy enough to change heavily the last arc.

Well, there's a lot of differences like this. They still reunite in japan in 1929, victorique's hair color stil change, both brian and Cordelia dies for example, but the path to reach this is quite different. There is an additional part in manhattan in 1934 after their reunion in 1929 as well, where they're running a detective agency named "gray wolf detective agency".

If you want more specific info, you can ask, but since I finished to read the series last year, cannot promise you that I'll remember everything. As a general rule, any scene that seems weird or illogical -if you think about them- in the anime (there's a lot, especially near the end) were either created by the anime staff, or the anime missed a specific scene related to the explanation of them.