I have enjoyed the books, but like many alternate histories I do not think the world would be so similar to our own.
Basically for an RPG a good regency world book would cover most of it – and that would cover many potential sources, the nice thing about a historical setting is that you do not need a specific licence to cover it as long as you file off the serial numbers. A good regency book would cover Sharpe, Hornblower, Rmage, Brigadier Gerard, Bolitho and all the others, even Jane Austin's books for goodness sake!