The Original Sinners: read The Siren before the prequels

A prequel is not always an invitation to start earlier. Tiffany Reisz explicitly tells first-time readers to read the Red Years before the White Years. I would take the person who wrote the books at her word.

The series centers on Nora Sutherlin, an erotica writer and dominatrix, alongside a club owner and a priest. That premise should tell you whether this is your kind of complicated. It is a poor choice if your only requirement is a tidy two-person courtship with no difficult edges.

The order protects the reveals

Books one to four form the Red Years. Books five to eight form the White Years. The author explains that the later group also continues events after The Mistress, which is why sorting the story into a strict timeline can spoil the experience. The ninth main novel is The Priest.

There are also novellas, collections and other stories. Keep those on a separate list for your first pass. Completing the main sequence gives you a stable reference point; trying to insert everything immediately is a reading project of its own.

Know which sort of difficult you enjoy

I would choose this for a request about recurring characters, BDSM and religious conflict. I would not use it as a generic introduction for someone who has only asked for 'a bit more spice'. The subject matter and relationship structure deserve a more specific conversation than that.

• Religious themes. The priest is part of the premise, not a passing reference. If that subject is uncomfortable, choose a different setting.
• Power dynamics. Look for detailed content notes about the book you plan to read. A single label cannot describe every relationship in a long series.
• Expectations. Our genre guide explains why heat alone does not tell you what sort of romantic resolution to expect.

Two books called Priest, two different authors

Reisz's The Priest belongs to Original Sinners. Sierra Simone's Priest collection is a separate work. Search with the author's name attached. That tiny step saves you from picking up the wrong priest, which is an unusually specific catalog problem.

If what you actually want is a club setting and a fresh central relationship in each book, compare Masters of the Shadowlands. It answers a different request. Neither series needs to be declared the winner for the comparison to be useful.