Just finished my latest Simon Scarrow novel 'The Legion'. This is in his Roman Empire series following the adventures of Macro and Cato, now both Centurions, around the Empire's wars.
This episode takes place in Egypt. Cato and Macro are chasing the slave pirate Ajax along the coast where he is impersonating a Roman unit and destabilising the Empire's hold on what was a vital province.
He is eventually cornered by the flotilla led by Cato, but escapes overland. Ajax heads for Nubia and joins up with the Nubian army that has launched a major attack on the southern provinces. Cato and Macro are ordered to join the 22nd Legion and Cato ends up commanding the legion after the death of two previous commanders.
Scarrow is a master story teller. His books have real pace and his heroes have that anti-establishment edge that make them interesting and powerful characters in their own right. The model is of course Sharpe, just back a few centuries. Be warned this is very difficult to put down!