I have favourites, too many to mention, from various interesting genres.
But easily by far the best book I have read and which everyone should read is The Brothers Karamazov of Fyodor Dostoyevsky. Writing at its best IMO. Usually have it hard thinking of anything as the absolute certain best and such, but this one is by some margin.
Another dinstinctive favourite, which is one I re-read every year (when I normally never re-read books), is Oscar Wilde's Picture of Dorian Gray. And I re-read it because it doesnt give you the sense that you know this all already as with most other things, but that his prose is so insanely rich and witty that you feel you are reading it for the first time ever time (its all about the prose for this wordsmith, the plot isnt really as important).