Certainly you can't trust web site categories or the physical bookshop location.
Likely if you want actual Napoleonic War history book, neither "The Infamous Army" (Heyer) or Temeraire (UK title, Novik, some versions "His Majesty's Dragon") is what you want. Though the Heyer "Romance" does really have things the people involved with Waterloo wrote and is relatively historical on the battle.
Temeraire was real ships
https://en.wikipedia.org/wiki/HMS_Temeraire