ebrary offers a 3USER perpetual license for some ebrary books.
If you purchase a book as 3USER, it is equivalent to purchasing 3 single-user copies, but at a significant cost savings. Up to three users will be able to access the book at the same time.
For implications/settings regarding limitations on full-document downloading, see:
Important! The 3USER purchase option is NOT available on the partners site, ONLY via the Admin tab on your ebrary site