I Know This Much is True by Wally Lamb

This epic 800+ page novel deals with the dual plights of twin brothers - one with schizophrenia and one without. Domenick has spent the majority of his life protecting and simultaneously hating his brother Thomas because of his disease, to the point where his own life is nearly destroyed. The narrative is told through flashbacks and also features segments of the twins' grandfather's memoirs (and though he died before their birth he, predictably enough, has foreshadowed a lot of the novel's present). The themes of love, loss, familial obligation and personal responsibility are boundless here. Throughout the book, you're not really sure which brother you pity more and though Lamb probably could have cut out about 100 pages or so, it was still a compelling read.