It all started with Julien van Remoortere's Belgian Beer Book. That sparked my interest in the broad spectrum of beer, in particular from Belgium and later also Germany.
A few special features are the older Grolsch booklets that I received from a colleague (who used to work there). I also came to Ghent a number of times because of my hip surgery and a visit to the bookshop also yielded quite a bit.
Of course, the collective can easily become larger, because there are many books nowadays with complete lists of different beers, but the book has to offer me extra information in the field of the brewery, the region, the beer style, history, etc.