"War and Peace" (Lev Tolstoi)
"Karamazov brothers" (F. Dostoievski). It's a too long novel. You may read some paragraphs: the most sublime, plenty of spirituality
.........I read years ago John XXIII's Decalogue and it changed it my life. It's very short and very impressive. To everybody who believes in God (catholics, protestants, orthodox, jews, muslims, mormons etc).