Often what makes or breaks a book is the main character. Some characters are placeholders, put there for things to happen to. But some leap off the page in three dimensions, tearing through the story, knocking other characters on their rear, and staying with you long after you turn the last page. One of my favorite examples of this is the Bloody Jack series by L.A. Meyer, well worth reading for history buffs, sailor wannabes, and anybody who likes a ripping good yarn.
Bloody Jack starts out the first book as Mary Faber, a clever urchin from the streets of 1804 London who sees the chance to better herself. So what if that chance takes the form of pretending to be a boy named Jack aboard one of His Majesty's naval warships? She's not going to let a little thing like gender stand in her way.
Over the eight books in the series, she gets in all manner of trouble, including piracy, kidnapping, sailing down the Mississippi, treasure hunting, all the while remaining faithful (well, mostly) to her beloved Jaimy, a fellow sailor on her first ship.
Jacky is a delight and a pain both. She's impulsive, often thoughtless, even more often stubborn. But she's also warm-hearted, generous, clever, and daring, and she will steal your heart.
Then hold it for ransom.