The Bell Jar by Sylvia Plath
Read this on my Kindle. It's one of those classic books you feel you probably should read at some stage in your life.
Esther Greenwood on the surface has everything - boyfriend, good looks, exciting summer job, scholarship at a top college. But inside she's struggling to cope, and succumbing to a deep and debilitating depression. The novel tells the story of her fall and subsequent struggle to climb up out of it again.
As you might expect from that brief synopsis, it's not what you might call a cheery tale. It's beautifully written and the subject matter is handled so well if you didn't already know you would guess that the author had some experience of depression herself.
Worth reading for the beautiful prose and economical description, but I'd avoid it if you need cheering up yourself.