The Private Library of Emperor Franz I (17681835), later known as the Fideikommissbibliothek of Habsburg-Loraine, is considered a prime example of an imperial book and graphics collection and has been largely preserved in its original form to this day as a special collection of the Austrian National Library. At the same time the rich collections and the fate of the library have remained widely unknown to the scientific community, since large parts of its collections remained inaccessible until now and the history of the library has as yet not been duly reviewed. Co-authored by Thomas Huber-Frischeis, Nina Knieling and Rainer Valenta the present paper seeks to deal with this academic void in comprehensive manner. It is not merely conceived as library history in typically chronological form, but based on a broader scientific approach. Several interdisciplinary issues are discussed in accordance to the various aspects of the collection. Thereby this monograph of a great book collection provides a case study for many important topics of library history from the end of the eighteenth to the beginning of the nineteenth century. With this respect it supplies basic research, based on a broad amount of sources. Beginning with a general introduction the main part of the book is composed of eight substantially self-contained chapters (29). First of all the socialisation and education of the monarch as well as the example of the private library of his parents are thoroughly discussed, followed by the reconstruction of the primary holdings of his own book collection. Chapter 3 is particularly dedicated to the library staff, after dealing with some further aspects concerning the life of the emperor. Chapter 4 reconstructs and analyses the no longer existing library building within the context of architectural history. The funding of the library in terms of its explicitly private character and the growing of its holdings by means of different ways of acquisition (book selling, auctions, gifts, purchase of whole collections) are the topics of the following parts. Thereby the composition of the library has been examined in terms of how strong various disciplines were represented at several specific dates. A separate paragraph is dedicated to the rich amount of historical catalogues. The last two chapters provide a twofold approach to the problem how the library can be examined within the historical context: On the one hand the effect of historical milestones on the holdings of the collection is analysed statistically and on the basis of selected examples; on the other hand the library is compared with other contemporary book collections.