While the book was an interesting read I do not, however, subscribe to most of what its authors say. Like others, 7 hours sleep is adequate for me. I certainly do not require more. The only piece of information which, I think, benefitted me was that on darkening one's room. Having said this I can still sleep well in a lit room or even during daylight. I remain unconvinced about the theories expounded by those authors. My style of sleeping differs and I follow the needs of my body and not what others try to tell me.

Interestingly, my wife's sleep-pattern closely resembles that recommended in this book. She needs the minimum of 8 hours undisturbed sleep otherwise she is tetchy for the remainder of the following day.