I've also noticed this problem, on Jolla 1 and Tablet, of Android applications not showing up at all, or if they do show up they don't have any icon. Never managed to fix it, unfortunately. If you installed Aptoide via the Jolla store, you should be able to open it from there, otherwise, good luck, I have no idea.

As for your problem with the books not showing up, you should read its description again, they're supposed to be inside either the Downloads folder or inside Documents/Books: https://openrepos.net/content/slava/books