A Close Third
I do a lot of reading on my phone, both with ebooks and audiobooks. Thus, were I to say Overdrive is my third choice when it comes to book apps and leave it there it would sound too negative to truly represent my opinion.
Overdrive is not Audible or Kindle (both absolutely stellar apps in their own rights) but its functional and covers niches that these others dont: most importantly, borrowing ebooks and audiobooks from my local library. Im typically more likely to return to an old favorite in my Kindle or Audible libraries than I am to start a new book on Overdrive, but this app is still a great addition to any bibliophiles utility belt.
Spideycow about
OverDrive: eBooks & audiobooks