The only way I can think of is to wait till the books expire, and then borrow them again.
(If the library has extra copies and you have extra free loans, you may be ableto borrow them again at once).
The anonymous id is a complete stupidity; it does have minor benefits for people who want to get up and running very quickly, but the dis-benefits and confusions far outweigh the benefits.
ADE does give warnings about it, but they are not nearly strong enough for people to appreciate the implications.