Untimed by Andy Gavin is an interesting adventure through time. Charlie follows a strange, robotic man through a hole in space/time and meets Yvaine. Together they meet notable people from history including Benjamin Franklin and his son William. Unwitting changes to history result in timequakes, and the larger the change - the larger the quake. At the end of the story the stage is set for another adventure.
Gavin has thought up some unique twists to time travel: boys can travel the time stream in one direction, girls in the other, and the mechanical beings Charlie and Yvaine call Tick-Tocks can travel either way. Time travelers are hard for ordinary people to remember and nothing they write down survives to give away the secret of their existence. His addition to the genre is fresh and entertaining. I would recommend it to teens, but not younger readers due to some adult situations.
Check out the author's website for more information about the book and about Mr. Gavin. There is also a short trailer for the book.
I read an e-book version provided by the publisher through NetGalley, but the paperback version is available in stores and there is a Kindle version, too.