Spanking, spanking and more spanking.
[This review discusses the whole series.] Dragonmaster was probably the best book in a strong series. There are some weaknesses, and I didn't like one of the books, (Peasant Farmer), but for erotica focused on spanking, it's the most enjoyable I've found. In most books like this, the world-building and often the plot itself are perfunctory. Not so here: the fantasy elements and the plots are very complex and absorbing. The culture and politics of the world are explored with a lot of details, providing openings for new books in the series.
The books depict a culture where women are legally chattel, where girls are raised to submit completely to the males who "own" them, and daily spankings are considered normal and necessary. (Hopefully that description will tell you enough of whether you will like this book or not.)
But unlike some books out there that depict the male using sadistic spankings to utterly crush a woman's will, these books explore a form of heavy discipline that is erotic and loving, even affectionate. And when I say explore I mean that exactly; the books are surprisingly insightful about the complexity of the feelings involved for the females (the book are all first person from the female's POV), how desire and fear and anger can war with each other, how being disciplined can arouse feelings of safety, fulfillment, and belonging. The metaphorical parallel with the dragons/dragon master is used throughout to excellent effect. Though the males demand complete obedience and dole out heavy punishments when they don't get it, the females are not cowed at all: they are funny, engaging, and very much effective agents in their world.
I would mention a few complaints: though most of the books are fairly well-edited, especially by the genre's usual dismal standards, they are poorly formatted--at least for my Kindle--a distracting annoyance. The final book, The Queen, while otherwise very strong, has a number of minor plot holes/ inconsistencies (what is the gender of the queen's baby?). It also makes use of some glaringly modern expressions--"you guys!" "I sucked at that"--which are painfully incongruous with the books' overall style.
But all in all, as spanking fantasies go, you will not find better.