How spicy is Twisted series by Ana Huang?

I have heard so many great things about this book series but when I checked the website of my local library they have categorized it as erotica, which surprised me because I didn't think it was that. I like romance books but don't like it when they are way too spicy and I would definitely not want to read pure erotica. I have read many romance books which are spicy, but usually I can get behind it although I prefer closed door. IMO, "It happened one summer" by Tessa Bailey was too much for me, for reference. THAT, I would label as erotica because it was barely even romantic.

EDIT: Just realized I missed a 'the' in the title