I personally listen to Audiobooks, mostly adventure / tale or similar. I find that it needs to have a dream like quality. Jules Vernes is great for it, the Count of Monte Cristo was a delight. I don't really follow the story as I miss basically more than half of it. Steer away from books where there is too much "action" ( LOTR was a total failure ) or too realistic ( you don't want some Houellebecq in your dreams ).