Why did books include CD-ROMs, and what material would suit one in a naval-history book?
Short answerThey carried large tables and appendices that were useful to researchers but impractical to print; today a website or QR code serves the same role.
NotesThe book's tables nearly appeared on an interactive disc. A doctoral thesis from the same research already used a CD for appendices because printing the underlying data would have added roughly a thousand pages. The format separated the readable argument from the evidence-heavy reference material. Modern books achieve the same purpose through web links or scannable codes rather than physical media.