I don't know if Amazon will publish it, so…
One Hundred Strokes of the Brush Before Bed, by Melissa P.
Not hot enough for one-handed reading, not intelligent enough to need a brain
"A girl who loves herself doesn't let her body be violated by any man whatsoever without a specific reason and without any pleasure."
Quite: casual sex can be delightful, but if it contains no delights for you, don't do it! This is the big difference between this and, say, Catherine M's memoir that others have compared it to.
The problem is that it takes about two years into the diary for the protagonist to write that. Unfortunately, by that point I'd lost any interest in the characters. She's looking for love via casual sex, they're inevitably looking for a compliant set of holes.
Eventually someone decides they love her, but – even in such a short book – I had to skim backwards to work out which one it was, and didn't care enough to bother.