Ponygirls of Irontown is the second Irontown book. I did not read the first, but it does have some similar elements of her Alice books, institutional slavery, and the like.
The book centers on a Ponygirl and Pleasure slave, Beauty, and her owner, a young lady named Samantha. Samantha is young, impressionable and immature, but she and Beauty do fairly well together.
Sam makes mistakes, and ends up in hot water, causing Beauty to have to be loaned out until Sam can return. Shenanigans ensue, the BDSM scenes are smokin' hot, and the bad sorts get their comeuppance in the end.
I really find the authors descriptions of scenes to be remarkably sexy.
4.5 stars for this one. Almost 5.