It's mindbogglingly complicated to 'release' a book. First, I have to add it to my library to generate a BCID. Then, I have to write a journal entry. Then, I have to add release notes, which is a multi-step process involving a second journal entry.
WTF. Journal entries? Four-page web forms?
When is someone who happens upon a registered book supposed to use bookcrossing anyway? When they find a book? When they have read it? When they release it again? Are they, too, required to make multiple journal entries?
Almost everything should be optional. A book needs a unique identifier (the BCID), maybe a QR Code, and then the only required element should be the location and an indicator for "picked up at Location" or "set free at location", ideally with a nice Google Maps integration, and perhaps even a mobile app.
Bookcrossing should be fun, quick and intuitive. It shouldn't feel like a bureaucratic chore. Please, please, please fix your site so it doesn't make potential users give up in frustration. Making it mobile friendly is nice (the web design feels about 15 years old by now anyway), but really, you need to fix the obsessive bureaucracy and make the website simple and fun for impatient users.