I've been reading the Flashman books for close on two decades now, after learning about them in an interview with Richard Lester (who directed the disappointing movie version of Royal Flash). I can say with certainty that George MacDonald Fraser significantly influenced not only my writing style but also the way I view the world. Fraser taught me to reject sugar coatings, mindless patriotism, and deification of historical figures, and to look at past events with a new and critical eye. Note that most heroes ARE anti-heroes to some degree; they just had friendly biographers to hide their flaws. The genius of the Flashman series is that the heroic/mythic veneer is stripped away to reveal the human underneath. (Flashy, of course, takes roguishness to an outrageous degree, which is a major reason why the series is so funny, though sometimes the laughter is shocked laughter.)
As for the writing, well... IMHO, Fraser is one of the best writers of the late 20th century. Nobody does battle scenes as well as he does. No one explains political motivations as well. Nobody makes history more palatable or weaves it into the story so naturally. And there are few characters as well drawn as Flashy, who is strangely likable despite his behavior.
For the record, I'm a woman, and I don't have any problem with the depiction of women in this and the other books. It's fiction, and Flashy's behavior has to be taken in the context of the times. (Frankly, if he'd behaved like, say, the wholly unbelievable folk who populated the historical travesty that was Dr. Quinn, Medicine Woman, I'd've been bored stiff after three pages.)
So read this first book to familiarize yourself with the character, but know that it isn't the best-written of the series. Fraser really settles in with Flashy's voice in the second book, Royal Flash, and just gets better from there!