Bookshelves never took off like we meant for it too, but also it create a lot of confusion with the Review Team. New members think the two things (Bookshelves + The Review Team) are much more connected than they are, and do things like get frustrated they can't download the book they selected for review from the Bookshelves page. To avoid this confusion, I think the best thing to do is just move Bookshelves to a completely separate website, so it comes off as a totally different thing/service which it effectively is. The data can still sync between the two like it does now (e.g. a book automatically gets add to a user's to-read shelf if they read it via the Review Team) but other than there is little to no connection from the perspective of regular users.
I'm also marking this as #TimeSaving since the confusion the current system causes ends up wasting a lot of the customer support staff's time to help users who get confused by the current system.