BookBrainz is described as 'Project to create an online database of information about every single book, magazine, journal and other publication ever written. We make all the data that we collect available to the whole world to consume and use as they see fit' and is an website in the news & books category. There are more than 10 alternatives to BookBrainz, not only websites but also apps for a variety of platforms, including iPhone, iPad, Android and Android Tablet apps. The best BookBrainz alternative is Goodreads, which is free. Other great sites and apps similar to BookBrainz are Open Library, Google Play Books, Tome and ReadHero.
While BookBrainz is currently in its early days, Open Library benefits from an already big library with options to borrow the book from a library or buy it from elsewhere. It's much more complete and usable.