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You could always look at all this stuff from the perspective of the armchair/popular scientist. In which case, we can recommend [[Why Women Have Sex: Understanding Sexual Motivation from Adventure to Revenge (and Everything in Between) by Cindy M Meston and David Buss]]. But - if it's just sleep you're after - try [[The Secret Language of Sleep: A Couple's Guide to the Thirty-nine Positions by Evany Thomas]].