I've been following this series from the beginning and it has kept getting better and better throughout. I don't follow many series and easily get bored with them, so this is a real exception. It has elements of Mystery and Thriller and even a touch of Romance, but technically it's Science Fiction because of the time travel.
Only there's no machine. The Time Shifters can slip through time or across distance at will, but not at the same time. And they can only move forward and backward within their life span. It's a very original concept and well executed.
I'm both looking forward to and dreading reading the last episode. I'm going to start today. Dreading it because then it will be finished!
I hope this author writes more. Oh and the paperback version is in two omnibus editions and called The Time Shifters Chronicles volumes 1 & 2. I'll add the second one to the database, the first one is already there. The series is also in audiobook.