We're big fans of fantasy novels! I love that Yoto has the Chronicles of Narnia, Harry Potter, His Dark Materials... such amazing classics.
I noticed there are some Terry Pratchett stories for young readers (The Carpet People). Would it be possible to have the Tiffany Aching series? They're so funny and brilliant!
Also, a bit darker but very good, The Spook's series by Joseph Delaney would be great.
Finally, I would LOVE it we could have The Hobbit read by Andy Serkis, because it's the most amazing audiobook I've ever listened to - but I don't know whether Yoto can buy the rights to that and sell the cards.