Following technical developments digitising of printed information is being done on a large scale in many countries. Publishers and libraries are exploring a range of technical approaches for creating digital documents from books. In part this activity may be motivated by curiosity about the feasability of new electronic concepts. But in an increasing number of cases a very practical approach is underlying present projects of so-called retrospective digitising. I will concentrate on libraries here. Today users request books, journals or photo-copies by the way of interlibrary loan or other document delivery services. Libraries with large holdings and with users well beyond the campus try to keep up with this ever increasing demand. However, this heavy use of library holdings is damaging books, which are out of print in most cases. In addition there is the threat of the brittle paper phenomenon. Although it is well known by now to every librarian and remedies have been sought intensely for more than two decades, it is still far from having been tackled.