When collecting books, first editions are often more valuable than later editions, so it’s helpful to know how to identify them, but the answer is more complicated than we expected.
According to the page “Identifying and Collecting First Editions” on AbeBooks.com, in the publishing industry, “first edition” covers all copies of a book printed from the first setting of type. If revisions are made, the revised book is the second edition, and so on and so forth. The first set of books printed is called the first printing, or first impression. If these all sell out and the publisher decides to make more copies, the second set is the second printing, or the second impression. So something marked a “first edition” may not have necessarily been part of the initial print run – it could be from a later printing, but before any revisions were made. Collectors are generally most interested in the earliest copies published – so, the first printing of the first edition – and that’s often what they use “first edition” to mean.
Official Price Guide to Collecting Books: Sixth Edition, written by Marie Tedford and Pat Goudey, and First Editions: A Guide to Identification: Second Edition, edited by Edward N. Zempel and Linda A. Verkler, both give tips on identifying first editions. Some publishing companies will include information on the copyright page such as “First edition, First printing,” or “First published 2007,” which makes it easy, but some give no indication. Sometimes it’s only possible to tell that something is an early edition because the collector knows what to look for, such as a certain error that was later revised. For example, Tedford and Goudey use one of Laurie R. King’s books as an example. She wrote her dedication in Hebrew and in the first edition, it was printed backwards.