The term "artists' book" is a translation of the French livre de peintre and refers to texts illustrated by artists of the 20th and 21st centuries, who often arrive at interpretations of the texts by free association. Text and images are combined to form a new artwork.

Ars librorum denotes bound and printed books decorated by an artist. Here, too, it is acquisitions by Erhart Kästner that form the core of the collection. Their more typically book-like character distinguishes them from the artists' books. This applies especially to the 20th-century hand-printed works, which are signed and published in small editions. Besides illustrated books, this section also includes works featuring outstanding typographical design.

These holdings grew considerably in 1995 when the HAB acquired a collection of 303 hand-printed works and illustrated books assembled by Jürgen Eyssen (1922–1988) primarily representing book art of the first half of the 20th century.

Altogether, the collection comprises well over 4,000 works by a range of well-known European and American painters and sculptors such as Arp, Beckmann, Bonnard, Braque, Chagall, Dalí, Derain, Dine, Dubuffet, Ernst, Hockney, Johns, Maillol, Miró, Matisse, Motherwell, Laurens, Léger, Picasso, Rauschenberg, Tàpies and Wols.