Battle Lines (Star Trek: Voyager, Book 18) by Dave Galanter and‎ Greg Brodeur - Paperback

During an expedition to an uncharted sector of the galaxy, the Voyager is captured and pressed into service by the Edesian Fleet in its battle against the enemy Gimlon, a situation that become exacerbated when Captain Janeway discovers that the Gimlon possess a super-weapon capable of destroying entire worlds.