I found this an enjoyable and fastpaced read, with engaging characters and a fascinating storyline.
To start with, the non-chronological order of events were a little disconcerting, rather like Audrey Niffenegger's 'The Time Traveller's Wife', which I personally found rather disjointed, although given the complexities and paradoxes involved if one were able to travel to any given time in the past, I understand why Mr Henry chose to record the narrative in this manner. However, after a short while I got used to events skipping forward and then back again and became absorbed in the characters and especially Mitchell himself. I emphasise travelling back in time because Mitchell is warned at the start of his adventure that if he travels beyond the point of his own birth, it will mean instant oblivion!
There is mystery and suspense, as well as a healthy dose of romance and the occasional touch of humour in this story which kept me guessing until the dénouement which actually caught me by surprise, although the clues had been there all along. The tale moves along at a fair speed and is as much a thriller as a Fantasy/time travel tale, which should widen its appeal even to those who are not normally readers of the genre. Being Welsh myself, I was delighted to find several 'Welsh' references - from Crystin (the Welsh form of Christine) who is an important character, to the term 'Amser' or 'Teithwyr Amser' which is the term the time travelers use. (Amser being time, and teithwyr, travelers)
I was sorry when this short read ended and look forward to reading the other books in the series when they are released.