I believe this book is the reason my son sleeps from 6:30pm-7am every night. So many Moms recommended this book to me so, now I need to pass it on to you. I suggest starting this book around 3 months.
The methods that it teaches you are so helpful. It's also nice to read real life testomonials from Moms that have been through the same thing.
Everyone comments on how happy and smiley my son is. I'm not giving this book all the credit but, it has definitely helped him get good naps throughout the day, sleep through the night and wake up feeling restored and full of energy!