Looking for stories where a character spends some time being very alone

I'm searching for any fiction or non fiction where someone does not have family or close friends. Maybe it's all of the book or maybe just a phase in the characters book.

I am flexible on what is considered alone. Books I already know of are White Oleander – foster system, learning to adapt to different social groups, takes a while to feel at home & settle somewhere, & Thoreau's Where I've lived & what I've lived for.