Surface and Destroy: The Submarine Gun War in the Pacific, by Michael Sturma;
Ghost on the Throne: The Death of Alexander the Great and the War for Crown and Empire, by James Romm; and
Plenty of Blame to Go Around: Jeb Stuart's Controversial Ride at Gettysburg, by Eric J. Wittenberg and David Petruzzi.
It may seem strange today, but during the First and Second World Wars, submarines usually had deck guns to engage in limited surface warfare. The Germans actually preferred the use of deck guns until the arly part of World War II, when advancements in anti-submarine measures rendered the tactic too dangerous. The US did use deck guns in the Pacific on a limited basis.
While Alexander the Great has been covered (and covered and covered and covered and ...) by authors over the centuries, the wars of his successors, called the Diadochi, have gotten relatively little, even though one of the Diadochi was Ptolemy, son of Lagos, who would start the Egyptian Macedonian Ptolemaic Dynasty that would produce the famous Queen Cleopatra. (Truth be told, the Ptolemaic Dynasty produced multiple Cleopatras.) I'm anxious to leard more about the Diadochi through Ghost on the Throne.
As for Gettysburg, I have never found that battle as interesting as the Vicksburg Campaign or the Chickamauga-Chattanooga Campaign, but Plenty of Blame to Go Around sounds like a great "sniper" book that I almost always find appealing.