Sex books for women are called something like:
Be Loved for Who You Really Are: How the Differences Between Men and Women Can Be Turned into the Source of the Very Best Romance You'll Ever Know
and show a hand-holding couple in soft focus (which almost doesn't fit on the cover because the title is so fricking long.)
And sex books for men are called:
GREAT SEX: A GUIDE FOR MEN
and feature a naked woman on the cover and are about 300 pages shorter than the women's book. Illustrated.
The great sex book talks about this study, which determined how certain scents increase bloodflow to the male genitals. Not only did they get volunteers to hook up their genitals to bloodflow monitors and get them to smell stuff. First, the scientists hadda use a "non-odorized mask" so they could record a "baseline brachial penile index" for each subject.
Scents that "worked"? Cinnamon buns, baby.