I'm not talking abouts apps that focus on community or your reading status like Goodreads, Fethir, or Leio.
Ultimately there are two main contenders if you want to catalogue your books.
I've had Book Track around for a few months and it's been in constant fast development. When I started with it the scanning was slow when it came to multiple books. You'd have to reinitiate an "add" sequence every time you wanted to add a new book. Since then this has been changed and you can add multiple books very fast.
The second contender is BookBuddy, which I have less experience with, but is really good too. I found that it did a better job at not duplicating book genre's that varied in capitalization. Where Book Track had AUTOBIOGRAPY and Autobiography and autobiography, BookBuddy only had a single category that encompassed all these books.
I understand that this is a data problem in the sources that each app chooses to use, but it's still annoying to have to clean up a bunch of data. This isn't to say that BookBuddy was without issues in data duplication though, it simply seemed to have less issues than Book Track.
One thing that Book Track did better than BookBuddy is in it's management of your wish list. Book Track allows you to tag items in your wish list, which lets me easily track which books need to go "to bookman" and which ones I've already put on "bookman hold". BookBuddy doesn't allow tagging of your wish list, so I've had to steal it's favourite functionality as a stand in. Books that have a heart on them have not been sent over to my favourite local bookstore on my hold list. Once they've been sent the heart is removed and I have a record of the books I've got waiting for me at The Bookman.
So for both apps I have issues, but given that I find the data in BookBuddy to be better, that's where I'm sticking for now. I also find that BookBuddy has better data density compared to Book Track. I hope that BookBuddy changes and allows tagging of your wish list items. That change alone would mean I wouldn't look longingly at the tagging of wish list items in BookBuddy.