There is no sex of the fantasy sort that e-mail is sometimes used for, part romance and part pornography.
Physical sex is restricted to what the two virtual lovers have with others' bodies off-screen.
It is appropriate, since Pi, the woman, is a budding philosopher and J.D., the man, is knotty-headed enough to be one. Mind wins out in this speculative fiction, which owes something to Milan Kundera's novels of thought and eros, and something to Diderot's philosophical romances. The bogging, set out in the first part of the book, begins with two traumas. These were her brain, her life, her talent, her future. J.D.'s trauma has been oozing up all his life.