I read this book years ago, working graveyard at Kmart to pay my way through college, so when I saw it available as a ebook at Fictionwise, I bought it and read it. It’s pretty cool sci-fi. It tells the story of a young woman named Rissa that grows up in a corporate-oligarchic world but escapes to the outer planets to lead a resistance against the powers that be. On some levels its pretty dated, technologically and politically, but it’s still good writing and a good story. It’s the first book of a trilogy.
City of Amathar 
More than a trilogy. Or he has at least more than one trilogy. I read a number of his books some years ago. Found them somewhat entertaining as pulp level sci-fi, but not great.
I'll have to look for the others. I've only read the three books. I agree with your assessment, but I have a fondness for pulp sci-fi and adventure. Sadly, Busby books are pretty hard to find. Hopefully ebooks will correct that.