The best Book apps right now are Slovo: Book Journal & Tracker, Bookyno - Book Tracker and Must Read, The Book Tracker, ranked by visit traffic and sponsorship on Censuus. Slovo: Book Journal & Tracker ranks #1 of 6.
Slovo: Book Journal & Tracker, Bookyno - Book Tracker, Must Read, The Book Tracker lead the field, ranked by visit traffic and sponsorship on Censuus rather than by editor picks. The full ranked list is below.
By visits and sponsorship on Censuus: the live traffic each app draws, plus paid boosts. A paid subscription raises an app's placement and is marked as such; it never fakes the underlying visit numbers.
Slovo: Book Journal & Tracker currently ranks #1 of 6 Book apps by visit traffic on Censuus. The position moves with the live numbers.