An adjustable book cover (10) comprising a front cover (12) and a rear cover (30) that is integrally attached to the front cover (12). A front cover retaining pocket (48) is attached to the front cover's inner surface (24), and a rear cover retaining member (70) is attached to the rear cover's inner surface (42). Attachment means (92) are located on the rear cover's inner surface (42) and the retaining member's outer surface (80). The book cover (10) is dimensioned so that when the book cover (10) is placed on a book (100), the rear cover's left edge (36) can be folded inward, which allows the attachment means (92) on the rear cover's inner surface (42) to interface with the attachment means (92) on the retaining member's outer surface (80). The rear cover's left edge (36) can be folded inward various distances to accommodate books of different thickness.