The Library Catalogue will tell you whether or not copies of a book are available for you to borrow.
If the Catalogue shows that all copies are already on loan to other users (see example below), please use the Place Request option to place a hold on the book you need.
This means that one of the users who currently has the book will be contacted by the Library and asked to return their copy early so that you may borrow it - keep an eye on your Library account and Queen's email for updates.
