My Bonny Light Horsemen, by L.A. Meyer

Jacky Faber was finally captured by British intelligence and instead of killing her made her a spy in France where she was to flirt with French officers to collect information.  When her cover was blown she disguised herself as a boy and joined the French Army as a messenger.  As a messenger she met Napolean Bonaparte and many other famous French military officers.

I liked this book because it is adventurous and unpredictable.  L.A. Meyer also builds characters better than any other modern author I know.

Two other books I would recommend are: Mississippi Jack AND The Hobbit.