What are some alternatives?
When comparing BookAuthority and appenguin, you can also consider the following products
Goodreads - See what your friends are reading.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Bookicious - Find the best new book to read with books collections for makers, founders and entrepreneurs.
Codefreebnb - Airbnb clone. Written with not one line of code
LibraryThing - A home for your books.
GoNative.io - Convert your existing web application into native Android and iOS