Derek Blass came to my notice with the excellent Enemy in Blue. Allegiance, in my opinion, is even better.
The action in this book begins about four and a half years after the events of Enemy in Blue and straight away you know that the events of that book have affected the characters and continue to do so.
Cruz Marquez, the lawyer, is now providing aid to mexicans attempting to cross the border and it is while he is doing this that he is captured by an "army" trying to stop the flow of immigrants.
I could go on but spoilers would ruin your reading experience!
Allegiance is, among other things, a story of consequences and that, for me, is where this author really excells. The events of Enemy in Blue hang heavy over the characters and the spectre of Sgt Shaver too. Some authors don't do this realistically but Mr Blass does it well.
This book is gritty, violent and, at times unbearably tense. The action starts early on and doesn't really let up much all through.
I compared his last book to the books of John Grisham. With Allegiance I feel Grisham will be looking on with envy.
This author gets better by the book and I'm looking forward to reading more.