When you first start collecting coins you will often hear the saying “buy the book before the coin.” This is said for a number of important reasons. Knowledge is an important part of numismatics and the hobby as a whole, and acquiring that knowledge can help collectors make informed decisions, which in the end can save money. A coin collector who does not invest some of his or her collecting budget in numismatic references is like a car buyer purchasing a car without a steering wheel.
Since references are so important in numismatics the references themselves also hold value, and can be collected as a separate specialty. Numismatic books are somewhat different from other collectable books, of which the highest-prized editions are often the first editions. For numismatic (and other nonfiction) books this is not always the case. First editions, while interesting, often contain outdated information and are no longer good as a reference work. Only the most highly regarded standard works will hold premium value as a first edition, and sometimes an updated second edition can be more desirable than the first edition. The quality of the (photographic) plates can also be a factor.