If you want too read them, it's probably best to start with Natural Selection which explains how Shepherd got his nickname during the jungle phase of SAS selection.
You can buy it in the US Kindle store BY CLICKING HERE
And in the UK Kindle store BY CLICKING HERE
At present I'm working on the brand new full-length Spider Shepherd novel, the 11th, which will probably be called White Knight. Hopefully it'll be on the shelves in the summer of next year!