This study concerns an inventory of books, dated 1428/29, inscribed in Sofia, Dujčev gr. 253 (olim Kosinitsa 265), fol. 290r. Although the text was obscurely published in 1886, the vicissitudes of this codex over the following century impeded further research and the inventory continues to be overlooked in studies of Byzantine libraries, books and reading. A new edition, furnishing corrections and filling lacunae, together with a first translation and palaeographical analysis, provide a foundation for introducing this rare document and re-evaluating its context and significance. While the limited prior scholarship generally presumed compilation in a monastic library in 1428/29 and pursued inquiries based on that surmise, examination of Dujčev gr. 253 draws attention to annotations by a member of the Laskaris Leontares family, dated 1431-1437,which place the codex in private possession during this period. A survey of thirteen extant codices variously connected to this distinguished aristocratic dynasty, c.1400 - 1455, elucidates acquisition, ownership and use of books in this socio-cultural milieu, with particular reference to this family’s history and social networks. Comparative assessment of this sample of thirteen codices and the 21 items recorded in the book-list of 1428/29 affirms the view that it relates to a private rather than an institutional library and distinguishes its potential value for investigating aristocratic book culture in the late Byzantine era.