Well I got it when DS was about 5 months old and a terrible sleeper and terrible napper (very short naps)
Here is how it helped me (but I agree, not a cure-all, but I don't think she ever claims it is--we still have bad sleep problems though)
1) watching for tired signs and getting him to nap earlier in the day, soon after he woke up. Using that "intervention" after 20 minutes to get him back to sleep so he would sleep longer. Now he takes 1 hour naps, sometimes 2 hour
2) Bedtime routine. We used to have a half-hearted routine and now we are very strict with it. He is pretty good about going to sleep at his bedtime, around 8pm.
3) The "gentle removal" has not worked so well with us. If I try he totally wakes up and sits up and crawls away, screaming. he doesn't just keep rooting like she says--he fully wakes up!
I am actually thinking of doing the "temperate" crying solution that she describes in the "if you are at your wits end" section because nothing else is working, which is kind of like the Dr Jay Gordon nightweaning plan. (DS is 10 months old almost now)
The main idea of the book is that you have to develop a plan for your family. This is kind of hard to figure out--there are no rules for it, just some guidelines. So I think it takes a lot of trial and error to figure out what works. And it takes a lot of time.
Our problem is that he keeps getting sick or teething just at the time we are starting to see some changes, so we're back to the starting point again. It is very aggravating! I'd suggest getting the book out of the library or used on amazon or something. You will want to xerox the log sheets.
Good luck!!