I got to say most of my favourite are children's books.
They would be all the Winnie the Pooh Books, I appreciate them more as an adult
And most of the Roald Dahl stories.
Most of my "adult" books are so difficult to pin down a favourite, as I prefer to have favourite authors.
Joyce Carol Oates, Faye Kellerman, Mary Higgins Clark, Chaim Potok, Jane Austen being some....
the latest book I can say I enjoyed over and above my usual pile has to be My Sisters Keeper !