There's no correct book about children's sleep - only the one that matches how you want to parent
The shelf runs from the entirely gentle, no-tears end to the structured, method-driven end, and both have books worth reading. The question isn't which is right; it's which fits your values and your child's temperament.
Which also means a book that made your friend's life easier can be the wrong one for you, and that isn't a failure of either book.
Read it as a set of ideas and a map, not a protocol to follow exactly - the families who struggle most are usually the ones trying to make a real child match a printed schedule. And if the sleep problem has a medical cause, no book on the shelf is the right starting point.
Source: babysleephelpcenter.com
The map, not protocol part is right. Our schedule book said nap at 12:30 sharp. My daughter had not read it.
raised mine with no book at all and he sleeps fine now. he's 30!