What's your favorite book(s) of all time?

Well, not sure if Light Novels are accepted, but Mushoku Tensei by Rifujin na Magonote is unquestionably my favourite. Whilst it's understandably critiqued for it's choice of unsavoury topics, it's the only book I've ever read that tells the story of a person genuinely learning from, and reflecting upon the mistakes they've made in the past.

Also Holes by Louis Sacher is pretty neato.