Pamela Stephenson, the wife of Billy Connolly, has written "the most comprehensive book on sex – ever", according to her publishers.

Stephenson, a comic actress who retrained as a clinical psychologist and psychotherapist, has received an advance from Ebury publishers for Sex Life, which will feature personal stories and offer practical guidance.

Connolly, who has been married to Stephenson for 20 years, once said he wished his wife would bring her work home a bit more often.

The book, the author's fourth, argues that sex lives are constantly evolving and that each stage is necessary and relevant.

Her commissioning editor Miranda West said: "The journey that Pamela will chronicle is epic and in many ways defines who we are. It is quite an undertaking, but the book could become a classic of the genre."

Stephenson starred in the 1980s TV sketch show series Not the Nine O'Clock News. Her first book, Billy, a biography of her husband, won the Book of the Year at the British Book Awards in 2002.

She wrote a sequel, Brave Mouth, and then a self-help book, Head Case: Treat Yourself to Better Mental Health. She also writes a weekly column, "Sexual Healing", in the Guardian and recently received an honorary degree from Aberdeen's Robert Gordon University for her academic work on human sexuality.