I'd been hesitant to reccomend this series for awhile, because it suffered heavily from publisher meddling. Namely, the series was intended to be three books and got split into six, with a lot of bridging "as you know" stuff that really irritated me. What I've linked is the remastered series, which takes what was six books and condenses it back down to three very long ones. The remastered series goes The Bloodline Feud, The Traders' War, and The Revolution Trade. At $9 apiece on Kindle, they're a steal, since you're effectively getting two books for the price of one.

The story starts as a pretty standard "woman finds her way to a parallel world", but it's very much a deconstructionist take on the concept, since it readily acknowledges how terrible the Middle Ages are. The themes of the book are economic, scientific, and political. Highlights include the exploitation of the power to hop between worlds and a really well thought out exploration by the author of what the power would really mean within the rigid rules system he's set up.

Personally I think it's worth reading for the end of the sixth (remastered third) book alone - when I got to it, I had to just set the book down and laugh and laugh. It's one of the better escalations of conflict I've ever seen done.

As another highlight, the main character Miriam is smart, motivated, and independent, which I don't think you see a lot with princesses thrust through a portal to another world.

(Also, this is the same author who wrote what I consider to be the seminal work of Singularity fiction, Accelerando.)