In a comment to A Database of Chess960 Start Positions, JHVN asked, 'Do you know of any other Fischer Random Chess Opening books other than the one on Lulu.com?' I can take a hint, so I searched Lulu.com, a well known site for self-published works, and came up with Search Results: 'chess960' (4 items). All four items, of which 'Mastering Fischer Random Chess' appears to be the primary work, were authored by Jan H van Niekerk. Unless I'm facing an extraordinary coincidence, it's a safe bet that 'Jan H' and 'JHVN' are one and the same.
Getting back to JHVN's question, I don't know of any other chess960 opening books. The standard work in the uncrowded field of chess960 titles is Shall We Play Fischerandom Chess? (on Amazon.com) by GM Svetozar Gligoric. It's a good book that deserves its own review in a separate post.
The only other English language title I know is Play Stronger Chess By Examining Chess960 (also Amazon.com) by Gene Milener. A crippled PDF version of the book, missing 80% of the pages, is available as PSCbyEC960.pdf on PlayChess960.com. The Amazon page has a review titled 'Comments from me the Author' that points to Castlelong.com, where 'a companion setup id conversion program is available for download'.
This program performs cross-referencing between chess960 setup id numbers from a variety of known systems. These systems include F9# used by Fritz9, S# adopted by Arena and some other chess playing programs, and our recommended R# "reciprocal" system.
According to the example on the download page, the standard numbering system that I use on this blog is what Milener calls S#. This must be named after Reinhard Scharnagl, its creator.