1 The Brothers Karamazov, Fyodor Dostoyevsky
Reason: the best book ever written about the human condition.
2 Iob, LXX
Reason: bad things happen to good people, quite often.
3 I Am a Cat, Natsume Soseki
Reason: comedy is good for the soul. This is the funniest book I've ever read. Cheating here, but I'd probably add Gogol as a next choice.
4 The Symposium, Plato
Reason: love. And I'm an only partially reconstructed platonist.
5 Demons, Fyodor Dostoyevsky
Reason: explains a big part of the 20th century. Makes 1984 look like crude propaganda.
8 For the Time Being, WH Auden