Contrary to widespread rumor, this is a far from bleak book. While every character has his or her own misery, and it all takes place in a place called something like "cattle-roundup-ville", the moments of religious ecstasy and moral clarity are heartbreaking in their frequency - it's hard not to wish that one had such bizarre events going on around one in order to prompt such lofty oratory.
The story involves Ivan, Dmitri, Alyosha, and Smerdyakov, four brothers with a rich but notoriously lecherous father, Fyodor. All four brothers were raised by others, Fyodor having essentially ignored them until others removed them from his care. In the beginning of the book, Alyosha is in the monastery, studying under a famous elder name Father Zosima; Dmitri has just left the army and stolen a large sum of money from a government official's daughter, who he has also apparently seduced, all while pursuing a lawsuit against Fyodor for his inheritance and canoodling with his own father's intended, the local seductress Grushenka; Ivan, the intellectual in the family, has just returned from (I think) Petersburg. Dmitri is violent and impulsive, referring to himself as an "insect," and gets into fistfights with Fyodor several times. Smerdyakov works for Fyodor as a lackey, having gone to France to learn to cook at some point in the past. It's unimaginably more complicated and digressive than all this, and just trying to follow this crucial sum of three thousand rubles through the story is almost impossible. But anyway, Fyodor is killed and much of the book hinges on which brother killed him and why.
When I first read this book in high school, my teacher (who was a devout Catholic, a red-faced drunk who wore sunglasses to class, and the most enthusiastic reader of Russian literature imaginable) asked everyone who their favorite brother was. Was it Ivan, the tortured skeptic? Dmitri, the "scoundrel" who tortures himself for every wrong he commits but can't help committing more? Or Alyosha, the saintly one who always knows the right thing to say? (Certainly Smerdyakov is no one's favorite.) At the time I went with Ivan - I was in high school, after all, and his atheism and pessimism were revolutionary to me.
But now Ivan seems rather selfish and callow, and I can't help siding with Dmitri, the one Dostoevsky uses almost as a case history of conscience. Like Shakespeare, Dostoevsky gives his characters all the space to talk like gods, clearing pages upon pages for their reasoning and dialog. Dmitri fumbles with Voltaire and is clearly not overly literate, but in some ways that's apropos, because his main problem is the constant internal conflict between his desires and his ethics which is only partly resolved when he chooses to become responsible for not only what he does, but also what he wants.
The most famous passage in the book, Ivan's tale of the Grand Inquisitor, is, to me, far less interesting than Zosima's meditations on the conflict between justice and the collective good. The elder Zosima is a kind of Christian socialist who grapples with the typical mid-19th century Russian issues of how to build a equitable society without the extremes of coercion that the Tsar used to turn to, while also ensuring public morality and avoiding the kind of massacres that characterized the French Revolution (an event that seems to have been even more traumatizing for Russians than it was to the French due to the enormous cultural influence France had there at the time.) Zosima's answer is unworkable and in some ways naiive, but the discussion is well worth it, moreso than Ivan's somewhat simplistic dualism of Christ vs. the Inquisitor. Dostoevsky was a cultural conservative in the sense that he was constantly renewing his commitment to the obligations imposed on Russians by the Orthodox Church. At the same time, he was committed to the pursuit of joy through kindness and community and a kind of interpersonal fair dealing in a way that transcends his political concerns and is inspiring to see articulated in the lives of people who are as confused as the rest of us.
It's a huge, messy book, but so worth the effort. It took me about three months to read carefully, though my reading has been flagging lately, as well. I read this while listening to Hubert Dreyfus's accompanying lectures at Stanford on existentialism and this book which are available on iTunes U, and even when I felt his readings overreached, it was a good way to reread a tough and subtle work like this.