You can probably borrow it for free at your local library, you certainly don’t need to own it.
It’s easy to follow, both of our kids were well sleep trained at 5 months. I’ve foisted it on three different friends who were struggling and they all turned it around within a week.
YMMV, all kids are different, but empirically this method seems to work best of the approaches I’ve seen tried.
Fresh book recommendations delivered straight to your inbox every Thursday.