A pre-publication state of a book. A galley proof edition has already undergone all basic edits for content and corrections, but is still prior to the final commercial production of a book. The term refers to the historic process of book printing using moveable block letters. The letter blocks would be laid into the galleys to that held the type, and the proof copy would be printed from those galleys. In modern times, the term is often fairly interchageable with uncorrected proof and advanced review copy. Galleys may be sent to reviewers and book stores as pre-relase promotion for upcoming titles. Those galley editions may seep into the used book market. Since the galley edition precedes the initial publication of the book, it may techincally be the first appearance of that book, and as such, could be considered collectible. Typically, the unfinished appearance of the book detracts from its collectiblity, but completists will seek all collectible editions, including galleys, advanced review copies and/or uncorrected proofs.