At 256 pages, it isn't really a little book but a good book about the uses of stationery (I consider it a kind of etiquette book of stationery except the kind associated with weddings, for which there's another Crane book). Since this kind of etiquette changes slowly, you're probably all right buying a used copy as long as it isn't too old.
Lists types of formal stationery and their proper uses and discusses the correct form and etiquette for invitations to social occasions, weddings invitations, announcements, calling cards, and business stationery-
This, along with its wedding version, "Crane's Wedding Blue Book: The Styles and Etiquette of Announcements, Invitations, and Other Correspondences", have been the standard for creating invites and stationery for many years. Trust me, there's not much that isn't covered in these two books for creating layouts for stationery or invitations. These give you a foundation for proper wording and order from all of the major stuff you'd expect to all of the little things that most of us never consider until we get a cranky call because we missed something or worded it poorly. By having something already in print you can show the customer for approval before you even start, you save yourself and your customers hours (or even days) of frustration.