British writer Scarrow (Under the Eagle) offers a second action novel set in ancient Rome, focusing on a key battle in Britain during the Roman invasion led by Claudius in 43 A.D., then turning to an attempt to assassinate Claudius. The first half of the book follows the adventures of Centurion Macro and his eager young subordinate, Optio Cato (both of whom played prominent roles in the first book), as the Romans try to outmaneuver the forces of Caratacus, king of the Celtic tribes of Britain, in a series of skirmishes along the Thames. The battle scenes are lifeless and generic despite the nonstop action, mostly because Scarrow offers little in the way of character development (most of the combatants are military stereotypes) or period detail (the contemporary colloquialisms offer some unintentional levity: "Just make sure you get some proper bloody swimming lessons," Macro chides Cato). The assassination conspiracy that takes up the second half of the book is far more interesting. Macro and Cato must get to the bottom of a plot involving fellow soldier Vitellius, a Carthaginian surgeon and Flavia Lavinia, a former romantic interest of Cato's. Scarrow deftly negotiates this tricky, labyrinthian story line, but his writing style remains pedestrian. Cato and Marco are one-dimensional, albeit fitfully amusing, protagonists. Scarrow will need to elaborate their personalities considerably if they're to carry the sequel that Scarrow foreshadows in this book's rather predictable conclusion. (Dec.)