Just considered my books.
I have a whole lot of books. I've lost or tossed even more over the decades, some of which would now be prized nuggets of homebrew history. As would all the discarded, early Zymurgy issues. Some are stored away, either obsolete or of limited interest. Some historic stuff like The London and Country Brewer, and a lot of technical papers, are in cloud storage.
The bookshelf I actually access holds technical works, both current and historic: Thausing, Die Theorie und Praxis der Malzbereitung und Bierfabrikation, 6th ed. 1907; Wahl and Henius, American Handy Book of the Brewing, Malting, and Auxiliary Trades, 1st ed. 1901; DeClerck, A Textbook of Brewing, 1957 English edition; The Practical Brewer, MBAA, 1977 ed.; Noonan, New Brewing Lager Beer; Briggs, Boulton, Brookes and Stevens, Brewing: Science and Practice; Kunze, Technology Brewing and Malting; and the BA Elements series is still on the shelf until space is needed.
But if I could only have one book, it would be Briggs, et al.
I think I might be a geek.