Probably will appeal to teens, especially males, this is a solid time-travel book, about three teens saved from death in their own times and recruited to be a team of 'timeriders'. Their job is to live in a time bubble which loops them through the same two days in NYC over and over, and look for differences caused by others going back in time and messing with the timeline. Then they are supposed to figure out when the change happened, and send their agent back in time to somehow fix the problem and restore time to its correct track.
There is quite a bit of violence in this book, and of course the time they are sent back to is WWII - doesn't every time travel book touch on an alternate reality when Germany/Hitler won WWII? In addition, the shadowy 'agency' they are working for is not explained well, and throughout the book is represented by an older man who recruits each of the teens and sets them up as a team, and then leaves them on their own. There is no way to contact the 'agency' and they are left with lots of advanced technology, with no explanation of such, or way to get more or fix what they have.
All in all, too many tropes and stereotypes for my tastes, with the ending looking dire and a complete 'fix' in the last few pages. Reads a bit like a videogame, so it will probably appeal to that set. I won't be reading further in the series, however.