G. A. Henty 
Beric the Briton [PDF ebook] 
A Story of the Roman Invasion

Take a trip back in time to witness the turmoil that gripped ancient Rome when the great civilization was rent asunder by slave rebellions and regional conflicts between warring villages. This thrill-a-minute historical adventure focuses on the central character of Beric, a young Briton boy whose tribe has recently been brought under the power of the Roman Empire.