I haven't quite decided if Timeless is your somewhat typical teen time-traveling novel or it's The Time Traveler's Wife for teens. But since I have yet to read The Time Traveler's Wife, I suppose I will go with the former. 
 Basically, Michele Windsor is forced to live with her wealthy, aristocratic grandparents she's never met when tragefy strikes. There, she discovers a diary that hurtles her back in time to the year 1910. Michele meets the young man with striking blue eyes who has haunted her dreams all her life - a man she always wished was real, but never imagined could actually exist. And she finds herself falling for him, into an otherworldly, time-crossed romance. She soon has to balance her modern life with her time-traveling escapades. When she stumbles upon a terrible discovery, she is propelled on a race through history to save the boy she loves - a quest that will determine the fate of both of their lives. 
 One thing I liked about Timeless, is that Michele gets into trouble. Why, you may ask? Well, a lot of these time-traveling novels have characters propelling through time and disregarding the fact that whatever they do in the past could affect their present, they almost never get into trouble. I mean, surely, someone would notice if you were gone half the time or night, and returning home looking worse for wear. So yes, Michele does get into a little trouble, so yay for realism. 
 Story-wise, it's a pretty good one. The characters aren't as well-developed as I had hoped but the plot sort of makes up for that. The romance between Michele and her blue-eyed man is pretty good. Their interactions, while few, are meaningful and you do sort of get the doomed-romance vibe from them early on. 
 The novel ends on sort of a cliffhanger with a few loose threads. I'm definitely eager for the sequel because I want to see how it all plays out as well as the mysteries involving certain characters solved. :)