What are the spiciest age gap romance books?

Of the 9 age gap romance books smutrecs.com has rated, the spiciest are Credence (5/5), Promises and Pomegranates (about 4–5/5) and Gravity (4/5). 6 of the 9 are rated spice 4 or 5, on a scale from 0 to 5.

1. 
   Credence by Penelope Douglas spice 5/5
2. 
   Promises and Pomegranates by Sav R. Miller spice about 4–5/5
3. 
   Gravity by Sara Cate spice 4/5
4. 
   Heartless by Elsie Silver spice 4/5
5. 
   Mercy by Sara Cate spice 4/5
6. 
   Right Man, Right Time by Meghan Quinn spice 4/5
7. 
   Brutal Prince by Sophie Lark spice about 3–4/5
8. 
   Eyes on Me by Sara Cate spice 3/5
9. 
   Something to Talk About by Meryl Wilsner spice about 1–2/5

Each book page lists the sources behind its ratings. Ratings marked "about" are estimates. How we rate