The Jack Reacher Series

I've just finished Lee Child's Killing Floor. I had read a couple of the later Jack Reacher novels, so I thought would go back to the start and read the uncompromising hero's first adventure.
My first surprise was that it was written from the first person perspective. The two books I had read previously were both written in the third person and it got me to thinking if I had ever come across that before in a series of novels. I couldn't think of a single instance.
I wondered why Lee had changed the style. I know from my own experience that seeing the story from your protagonist's point of view can restrict what you write. You need to let other characters tell parts of the story rather than let your reader see it first hand. It also places some constraints on the timeline of the story, it tends to unfold in chronological order as the character moves through the book. Did he change due to those restrictions or was it the reaction of his reader's that made him alter the style?
Regardless of the style, Jack is the kind of hero who walks a moral high wire. He is James Bond for the 21st century with a bit of the Littlest Hobo thrown in. He wanders through the towns of America righting wrongs, normally by shooting, strangling, stabbing and blowing things up, before packing his bag and heading off into the sunset.
The 'Killing Floor' is typical of Jack as he destroys a counterfeiting ring, killing every bad guy in sight and freeing the town from the adverse influence of the villain. His actions in this book are motivated by a very personal tragedy and that is maybe the key to the character in his subsequent thrillers.
Like Bond at his best, Jack's investigations are exactly the kind of escapism that results in the male readers wishing they were him and the women wishing they could bed him. Great fun and I will definitely be catching up with the rest of Mr Reacher's adventures.
I'd be interested in hearing from anyone who has seen a change of perspective from one book to another in a series or alternatively what style do you prefer in the Jack Reacher series?