We already got that in Forged in Fire. Well, it showed the transition from Styles to Sulu's command. I don't remember if Sulu went on any actual official missions though.I don't know if it's already been suggested but I'd like to see a book covering Sulu's first mission as captain of the Excelsior.
There was also DC Comics' "The Tabukan Syndrome" storyline, collected in trade paperback as Tests of Courage, which told a different version of Sulu's first mission as Excelsior captain.