This article deals with books pointing to Christian influence in the Viking Age town of Birka. Three aspects are emphasized: written sources, finds of parts of books and related objects, and illustrations as models for handicraft. Special attention is paid to technical details. It begins with mentions of books connected with missionaries. The information derives from documents by Rimbert and Adam of Bremen. Connected with books are some book mounts turned into pendants, found in graves, that are proofs of magic or Christian influence. Of major importance is the well-known “Birka crucifix”, where the image of Christ is covered with tiny silver grains and no cross is visible. The author is convinced that illustrations in a work by Hrabanus Maurus, De laudibus sanctae crucis, have been model for the design of the crucifix. Also a number of miniature shields and crosspendants could be traced to this publication. Some of them even appear to have been made with the same tool. Other pendants, such as a tiny reliquary, as well as serpents and miniature chairs, with obvious Christian background, are discussed.