trade paperback : Often used to indicate any paperback book that is somewhat larger than a mass-market paperback.

spine : The outer portion of a book which covers the actual binding. The spine usually faces outward when a book is placed on a shelf. Also known as the back.

4to : Or quarto. A term used generally to describe the approximate size of a book, a book that is about 10" to 12" tall and roughly squarish in shape. The term is based on the size of paper traditionally used by book printers which has been folded and cut into 16 pages.

marginalia : Notes written in the margins, or beside the text of a book by a previous owner.