Someone Else's Skin — Elizabeth Coldwell

An erotic novel with fantasy, time travel, BDSM and ménage themes.

When Annie Harrison is hypnotised for an article she's writing, she finds herself in the body of Jai Galloway, a 23rd-century eco activist who plans to go back in time and save the earth's atmosphere from being destroyed. Loving what her new body can do, Annie is soon living two existences - one with her kinky musician boyfriend and one in the future, where she learns all the tricks of sex as a man. But the more time she spends in Jai's body, the more threat she faces of being trapped there forever...