Specific but not to the extreme versions of novels are hard to find.

Any younger female + older male
Female submissive
Couple shares love + passionate kinky sex
Not in any extreme ways tho..
Examples: Man is NOT 54 and female 19
More like female 26 male 37
DADDY but no diaper stuff
ROUGH but consensual.

Source: reddit.com/r/eroticliterature/comments/ln0inv/specific_but_not_to_the_extreme_versions_of