That book is about mean reversion strategies. So, if you're not into this kind of strategy, you may not find it useful. Doesn't mean it doesn't work for others .
There isn't ANYTHING that "works for some and not for others". Unless you're claiming "some things work for those who understand and don't work for those who don't". No shit, Sherlock. DUH!
"Mean reversion" IS a thing. Just not reliable "when YOU need it".