Ask your partner(s) for consent, not mythological or supernatural beings.
I think that about sums it up.
On a more serious note, if/when I get any free time, a book called The Atheist’s Guide to Sex is my number one goal (or perhaps editing an anthology, if I can rope others into it). Think of the endless chapter possibilities! Secular sexual ethics, the effects of religion on sexual guilt, religious bullying of GLBT teens, interesting sex acts in other species, the religious right’s war on women’s reproductive health, giving “the talk” as a secular parent, bizarre sex stories from religious mythology… I could go on all day.
What would you want to see covered? …And do grad students ever go on sabbatical to write a book?