As someone who stares at screen all day, the read aloud feature in play books is a real lifesaver esp if you set it at high speed. It prevents my eyes from tiring too much. I'm sharing this for those who like me, also uses play books. It took some effort to clean the files, especially vol. 7 and 8 which were a mess of epub2 and epub3 standard put together.  If you want another series fixed so it'll work with play books comment here and I'll see what I can do.