A marvellous book all about the bookplate, or ex-libris, the small and often highly decorative label pasted into a book, most usually on the inside front cover, to indicate its owner. Although the earliest known marks of ownership of books or documents dates from the latter years of Ancient Egypt, and people would mark ownership in the Middle Ages with simple inscriptions, it wasn't until the advent of printing in 15th-century Germany that we see the development of bookplates in their more modern decorative form. One of the best known of these early German examples is the "gift-plate" of Hildebrand Brandenburg of Biberach to the Monastery of Buxheim (c. 1480), showing an angel holding a shield of arms. Many famous artists of the day got involved in these early designs, including Albrecht Dürer, Lucas Cranach and Hans Holbein. By the late 17th and early 18th centuries the phenomenon had spread to France and England, and by the late 19th century, with the publication of A Guide to the Study of Book-Plates (Ex-Libris) by Lord de Tabley, the study and collection of bookplates on their own terms began to gain in popularity, with societies being founded and dedicated journals published. As to why one might need a bookplate, the introduction to this volume explains it rather eloquently:
And now concerning the reasons for a custom which may be said to be almost as old as the printed book itself, and which is anything but on the wane at the present time. — Books are not consumable goods, but chattels intended to endure; they are at all times invested with definite intrinsic value, often with fanciful preciousness. But, to fulfil their destiny, they must consort with many people, and, during the inevitable changing of hands, may easily lose their way back to the rightful owner. This dread fate may overtake them even without any intermeddling of the traditional malice prepense of book-borrowers, for, after all, almost all books have numerous brethren singularly like unto themselves. And, having once lost their way, they might lightly find themselves established in new colonies, were it not for the safeguard of some unmistakable mark of ownership.
Thus it may be said that the primary object of an ex-libris, is precautionary against loss, by accident or through the negligence of borrowers ; (whether a book-plate has ever fulfilled that purpose is, however, an open question still). A second, closely connected with the first, is to secure the identification of a valued tome as part of a collection. A third and universal object of the book-plate is, as I have said before, to gratify the sense of possession by giving some kind of personal character to chattels which in themselves are only specimens of more or less copious batches, or (by a curious, though intelligible reversal of the same idea) by giving this character to a work which the present owner believes to be almost unique of its kind.
From this peculiar feeling, difficult to express, but which can be recalled no doubt by all book-lovers, this desire to invest books with some more "personal" character, depends the custom noticeable in so many ex-libris ancient and modern, of dovetailing with the plain statement of ownership some more or less original "sentiment," or some bibliophilic motto which denotes a prevailing taste or bias of thought in the owner.