My favorite book of all time, simply (for me) the best book ever written is "Le petit Prince" (The little Prince). What an heartbreaking, inspiring, humorous, and good book.
On the fantasy level, it's a trick question . Let's say "A Game of Thrones"/Discworld Pratchett books series (all of them, I can't decide which one is better ). Then Malazan series.
In third place (last but not the least) The wheel of time series and Sanderson cosmere books .
Yep, I cheated, but hey, I'm a Mat Cauthon fan so, it goes with it