I very nearly posted pics of the Bodleian but forgot. The Bodleian Library was the first library (1602) to store books on their ends rather than their sides, simply due to a lack of space, and there is currently around 140 miles of shelved books which grows by 2–3 miles every year.
Millions of books are stored in a warehouse near Swindon and the Bodleian is also a copyright deposit library, which means a copy of all books and periodicals published in Britain are sent there.