Books in St. Cross Library are arranged according to a subject classification called the Dewey Decimal System. It is often used in public libraries so you might have met it before. Within each section they are arranged alphabetically by the author's surname. All the books are catalogued on to the union catalogue, OLIS (Oxford Library Information System) and findable via SOLO (Search Oxford Libraries Online).
The majority of books are kept in the Lange Room (Class Numbers 000 - 899). There is a "self-issue" machine there so you can borrow books at any time; this room also has several desks and a large work table and has WiFi access for laptops. New books and the Display for the Term are on display here.
Books with class marks in the 900s (e.g. history, geography, archaeology) are located in the Library/Computer Room (No. 15) on the second floor. where there is also a self-issue machine.
The Librarian circulates a monthly list of newly-arrived books.