There are some beautiful aspects of the book that will always stay with me. The Grand Inquisitor monologue is captivating, Alyosha is a deeply interesting character, Mitya's stories of gallivanting on a troika through Russia, and everything that is Grushenka...
But as a whole, I can't say I understood it. I didn't understand how these characters came together, or how the ending tied these (albeit interesting!) stories together.
Karamazov was the first Dostoevsky book I read. When it came to The Idiot, I was shocked by how different the writing style felt. It flowed more, the dialogue drove a lot of the narrative, and it generally was just a lot less dense.
I'm hardly an English Major let alone a scholar of Russian Lit so I'm sure the thoughts here are pedestrian.