/lit/ - Literature

What are some books that will help retore my spiritual "spark"?
I used to have absolute faith that this life is not all there is, that death was only a door to a higher form of existence, etc. It brought me joy and helped me move forward in life with a strong optimistic outlook, nothing affected me too deeply because deep down I knew it'd all be fine in the end.
During the past few months it feels like I've been basically becoming a hylic NPC, I feel lost, depressed and doubtful, I find myself becoming affected by materialistic (in the conventional sense, not philosophical sense) issues I would've easily handwaved just a year ago.
I don't want highly sectarian books/scripture, I tried getting into organized religion and it didn't help me at all, so please don't proselytize.
Could I get some honest recommendations?