I can recommend almost anything by N. A. M. Roger (http://www.amazon.co.uk/N-A-M-Rodger/e/B000APIJRQ/ref=dp_byline_cont_book_1).
An ancestor of mine was a captain at Trafalgar - his ship's signal book is in the family - I'll take some snaps of it when I'm down that way next and perhaps upload them if they'd be any use?