The NDL Gallery (http://www.ndl.go.jp/en/gallery/index.html) now features an exhibition "Incunabula -Dawn of Western Printing-" in which you can see 13 incunabula and 55 incunabula leaves selected from 15 incunabula and 307 leaves housed in the National Diet Library. The exhibition also provides explanations of printing types, paper, printing techniques and other matters related to incunabula. A glossary, chronological table and a collection of links to other websites is also available. 

From the NDL Gallery "Incunabula -Dawn of Western Printing" 

Incunabula are books printed with metal type up to the year 1500. If you search on the database Illustrated Incunabula Short-Title Catalogue (IISTC), you will find 8,396 titles of incunabula printed in Germany including 1,087 titles with illustrative decorations. 

Printed books in early times were designed in the same style as the manuscripts of medieval times, with ornamental initials, border decorations and illustrative miniatures. Woodcuts were used for such decorations including printers' marks, ornamental initials and beautiful illustrations. Woodcut technique was frequently used for incunabula printed in German cities including Ulm, Nuremberg, Luebeck, and Augsburg, especially by printers such as Günther Zainer, Anton Sorg, and Johann Bämler. Later William Morris, a great lover of such books, printed a number of books with woodcut illustrations at the Kelmscott Press.

Full volumes (bound) of Der Bilderschmuck der Frühdrucke and the title page

Der Bilderschmuck der Frühdrucke is a series of research books which present thorough reproductions of illustrations (including border decorations, woodcut initials and printer's devices) used in German incunabula. The following images are  reproductions of woodcut illustrations appearing in Jacobus de Theramo's "Belial" printed by the Günther Zainer in Augsburg, 1472. "Belial" is a moral book widely found among the general public in medieval times, and more than 110 manuscripts and almost 40 incunabula of it are known to exist. Zainer's is the first illustrated incunabulum of "Belial."

The author Albert Schramm was an incunabula researcher who studied theology and philology in Tuebingen and worked for a library in Leipzig. He died with the work unfinished, and it was taken up and completed in 1943 by the "Commission for the Union Catalogue of Incunabula (Kommission für den Gesamtkatalog der Wiegendrucke; GW)" which aims to compile a thorough catalog of incunabula.
 

Illustrations from Der Bilderschmuck der Frühdrucke (vol.2) (Click for a lager image.)