Hi all!
Last year I sent some feedback to Forward Chess, which offers interactive Chess e-books. Recently their app got an update, which makes it possible to use Voiceover for reading the board, same thing that Chess.com did something like two years ago. I promised to recommend them, if they make that possible, so anyone interested in Voiceover accessible chess books, Forward Chess is for you. They offer free samples, so you can test it out before purchasing anything.
By the way, feel free to publish at this group your recommendations for accessible materials.