If you love the idea of a Time Patrol, but thought Poul Anderson's seminal take was too intellectual, you might want to check out Simon Hawke's Time Wars series. Though in this world, joining the army means you fight in historical wars so things can be decided downtime rather than in the here and now (27th Century), this is better explained at the back of the book than in its interior, as the story will have the heroes impersonate legends of the Middle Ages like Ivanhoe and Robin Hood to stop a rogue time traveller bent on taking Richard I's place and changing history. So it's Patrol kind of stuff, but more action-oriented - it moves at a fast pace, and Hawke knows how to withhold and reveal information to create page-turning suspense. Though there's talk of what would happen if history were changed, I'm not sure the stakes are all that well defined in this first volume, but my time travel brain certainly has theories. Suffering from too many epilogues, there's one in particular that's extended to the point where I now expect those characters to return even if they're not the nominal star of the book. (Frankly, there are a lot of fun characters in this, and I'm glad the author has deemed it important to tie up their loose ends after the "mission", but Lucas Priest, the lead, is pretty much a cipher.) There are a dozen of these, and I've been slowly picking them up where I can just based on the time travel theme, but I'm happy to say the first one was fun and that they won't linger too long on my shelf.