Book excerpt: Examining the roles played by the mistress and the concubine, this study also sheds light on commercial sex, the ready availability of which possibly protected the sanctity of marriage in the years preceding today's less holy alliances. The book shows how sex addiction cast its shadow over the 20th century--from the accession of King Edward VII in 1901 to his and Mrs. Alice Keppel's great, great grandchildren and to Charles, Prince of Wales and Camilla Parker Bowles today.