This book was recommended to me by a friend. I was looking for information about how to prevent overtiredness in my newborn, and to get an idea about their intrinsic rhythms. In contrast what the book offered was a load of rigid and prescriptive adult imposed routines, which completely lack evidence. I am sure they must 'work' to get a baby to sleep, but the long term emotional and mental costs are too much to pay in my opinion. She uses the word 'self soothe' incorrectly - babies don't learn to self soothe by not being responded to, they instead learn to behaviourally extinguish communicating their distress, so they become a 'good baby' in adult eyes. Learning to self soothe first requires many experiences of being responded to and soothed first, before we build the neural pathways to do it our selves.
Her routines go completely against breastfeeding advice for young babies (she advocates only demand feeding for two weeks) and she negates SIDS guidelines also.
If you are considering using cry it out, there are other books and websites that use more evidence and have more compassion than this one.