This is my kind of book: an epic family saga with a strong sense of place. I hate to give it only three stars, but I've had to conclude that while it has its strengths, it doesn't live up to what it could have been.
The Thorn Birds starts off excellently, detailing the day-to-day life of a family struggling to get by in early twentieth century New Zealand. It's well-written, it feels very realistic, and there's a strong sense of place. There's believable conflict among the family members without any of them being unsympathetic. There's an interesting and unflinching look at the effects of strict gender roles on women's lives: something we don't see in most historical fiction, which tends to feature the elite rather than regular folks. (I'll read about the regular folks, any day, and McCullough does it well.) When the family picks up and moves to Australia, I was still enthralled. I loved the descriptions of life in the Outback and was drawn into the family's story.
Somewhere along the way though, things went wrong. The characters' personalities and relationships began to lose credibility with me; several times I just couldn't swallow that people in these situations would relate to each other the way they do. Meggie's relationships with both her mother and her daughter felt especially bizarre, full of contrived antagonism far beyond what one would expect. (In Justine's case, evidently she dislikes Meggie from birth. Ooookay.) Meanwhile, some of the more colorful personalities, such as Frank and Luke, fall off the face of the earth, while the brothers lose what personality they once had and slowly merge into one person, as if McCullough changed her mind about how many brothers the story required but couldn't be bothered to get rid of the extras. As for the romance between Meggie and Ralph, while at first it raised some interesting questions, it never captured my emotions and became increasingly repetitive.
Which is not to say that this is an awful book, because it isn't. It's well-written and the thematics are strong. The sense of place persists throughout, and it's fascinating to see how the coming of new technology affects the Outback. The main characters are decently well-developed, and while the book is long, the plot remains interesting throughout. I finished it in a few days. Still, if you have not yet read the classic historical epics, like Isabel Allende's House of the Spirits or Margaret Mitchell's Gone With the Wind, I'd recommend going with those first.