This study explores the collection of Czech books in the Strängnäs Cathedral Library. The books were taken to Sweden as war booty at the end of the Thirty Years’ War and are today the most compactly preserved collection of books of Czech provenance in Sweden. This so-called war library, which the Chapter received as a gift from Queen Christina I, was not seen by the new administrators as an integral part of the Church’s property. This paper aims to answer two questions: First, when and how the Chapter’s mental barrier broke down; second, what factors played a role in the reorganisation of Cathedral Library in 1764–1765 and the selection of books for the auction sale. To answer these questions, I analysed the manuscript catalogue of the Cathedral Library from the 1750s and the printed auction catalogue of 1764. In addition, I surveyed preserved copies, particularly those auctioned by the Cathedral Library. My findings reveal that it took more than a century for the looted books to integrate into the new cultural environment in Strängnäs. Their merger with the original Cathedral Library did not take place until the 1750s and 1760s as part of a reorganisation aimed at creating a modern historical collection. This reorganisation included massive disposal of books, a large amount of which came from the Czech book spoils. The research findings also indicate that the war origin played no significant role in their selection and sale. The fate of the Czech book spoils in Strängnäs represents a complex case of incorporating books from war booty into a new cultural environment. The study is one of the first contributions to the question of the so-called second life of Czech book spoils in Sweden.