The latest book in the Young Lions books seems to be free at Amazon UK at present. I enjoyed the first book and made it through the second and third. I think probably YA is the right category as some of the story telling rankled me but not a bad yarn based in an alternative England where Germany succeeded in invading but failed to capture the whole UK.
Anyway the free book is
Young Lions feast
Strangely the first book in the series seems to be unavailable as a kindle book but is available in paperback.