The hesitation is understandable. The Brothers Karamazov is 900 pages long and begins with sixty pages of ecclesiastical debate. Crime and Punishment opens in a St. Petersburg garret in summer heat with a feverish young man who is going to commit a murder he has theorised at philosophical length. The names are unpronounceable, the characters refer to each other by several different forms of the same name, and every conversation threatens to become a theological argument.
None of this should put you off. Dostoevsky is one of the handful of novelists who genuinely enlarged what fiction could do — who understood that a novel could be the site of serious philosophical inquiry without ceasing to be a thriller, a comedy, or a love story. The difficulty is real; so is the reward.
Where to start
Start with Crime and Punishment
Crime and Punishment (1866) is the best entry point. It is relatively compact by Dostoevsky's standards, it has a single, clear plot engine (Raskolnikov murders a pawnbroker and then cannot live with having done so), and it demonstrates every characteristic Dostoevsky technique: the interior monologue of a mind in crisis, the philosophical dialogue between characters who represent opposed world-views, the sudden reversals and confessions, the atmosphere of St. Petersburg as a city that drives people mad.
Read it as a psychological thriller first. The philosophical dimension will take care of itself.
Then read The Brothers Karamazov
The Brothers Karamazov (1880) is the summit. Three brothers — the sensual Dmitri, the intellectual Ivan, the saintly Alyosha — gather around their contemptible father Fyodor Karamazov, who is murdered. The novel is simultaneously a murder mystery, a philosophical dialogue about the existence of God, a study of family and resentment, and a story of spiritual crisis and renewal.
The chapter called "The Grand Inquisitor" — in which Ivan tells Alyosha a story about Christ returning to Seville during the Inquisition — is possibly the most famous single chapter in Russian literature. It can be read in isolation, but it means more in context.
On the names
Russian characters have three names: given name, patronymic, and surname. They are also addressed by nicknames and diminutives. Raskolnikov is also Rodya. Alyosha is also Alexei Fyodorovich Karamazov. Keep a list at the front of the book if needed — most editions now include character lists. After fifty pages, you will stop needing it.
What Dostoevsky actually believed
Dostoevsky is not a Christian apologist, despite what some readers assume. He gives his most persuasive arguments to his atheists — Ivan Karamazov's challenge to God ("returning his ticket") is the most powerful case against God's existence in the literature of the period. What Dostoevsky believed is that the choice between faith and doubt is the central human choice, and that it cannot be resolved by argument alone. He dramatises the choice rather than settling it.
The Verdict
Start with Crime and Punishment. Be patient with the first fifty pages. Allow yourself to be absorbed. Then read The Brothers Karamazov, ideally the Pevear and Volokhonsky translation. These two novels will expand your understanding of what literature can do and what a human being can contain.