The first Flashman book -- or should that be the second, given that it's a spin-off from "Tom Brown's Schooldays"?
The idea here is that it's a 19th-century historical series along the lines of Hornblower, Sharpe and Aubrey, but with a main character who's thoroughly dishonourable and cowardly -- and, as a result, generally more interesting to follow around. This also allows more scope for entertaining ways of engineering Flashman from one notable engagement to the next...
This isn't at all the same kind of humour as McAuslan, and I wasn't convinced after finishing this that I wanted to continue the series -- but having acquired one of the later books by chance, I then went on to read the whole lot -- so don't write it off based on the first one (and, indeed, don't feel obliged to start here; the series wasn't written in chronological order, and you can quite happily skip around at random in it).
ISBN 0006511252.