Dostoyevsky takes you from the highest, wealthiest levels of society down to the lowest criminals and scumbags. Indeed, along with the narrator himself, the two main characters move between these very different societies. Both were born into money and privilege but choose to associate with the criminal underground of pre-revolutionary Russia.
These two young men are nihilists and seek to destroy society, but with very different methods and motivations. They act on the horrible impulses all people irrationally feel from time to time, but usually restrain. Because of this, though the book can be shocking (especially a chapter that was censored from the original version), but also perversely satisfying.
A lot of what makes The Possessed great is the narrator. He is an inquisitive observer who is in the center of all the action but doesn’t contribute to it. It’s strange that he seems to be everywhere and see all, but he mostly keeps his sympathies to himself. He would be somewhat of an unreliable narrator, but all the other characters unconditionally trust him and come to him to confess their sins and ask for advice. He is a masterful character – and because of Dostoevsky’s genius you hardly even notice he is there.
Dostoevsky gets a lot of credit for his three most famous novels: Crime and Punishment, the Karamazov Brothers, and the Idiot. All of them are great, as well as many of his other books, like Notes from the Underground. But to me, The Possessed is unquestionably the best of them all.