Best description I can think of is that the book is a cross between Napoleon Hill, Victor Frankl, and Eric Hoffer. Peterson writes a self help book based heavily on evolutionary biology and psychology, fundamental truths in religious myths (Judeo-Christian, Taoist, and Egyptian mostly), clinical psychology (both theory and practice), and a study of mass movements and modern political trends. The Bible plays a big role in the book-- he's not trying to get the reader to believe, but to understand that it contains important lessons about human nature expressed in mythological form. Early in the book he spends time attacking some of the dopier theories of the political left (the ones most leftists around here probably roll their eyes at). Later he explains this criticism in a broader form, and includes criticism of the alt-right.
One of the big themes is proper parenting is important and shouldn't be a secondary concern-- ever. My guess is that most IGxers will see some value in what he describes and proposes in these parts of the book, especially the attack on masculinity that he describes as occurring at even a middle-school level (if you see these negative influences on your kids, you may have to combat them). He balances this with a call for weak men to move out of their parents basements. While the book seems outwardly to be focused on men, his focus on the both the positive and destructive impact mothers can have is fantastic-- I'm not familiar enough with the psychological literature to say whether or not he's saying anything new here (I suspect he isn't), but he may be the first popular and serious modern author with stones enough to say it publicly. There's enough for reasonably well socialized IGxers to find value in too.
Like Hills work, the book is uplifting and presents a path toward self improvement; like Frankl's work it's dark (dealing with tough subjects like school shootings, depression, addiction, and suicide); and like Hoffer's work it looks at the flaws in mass movements and what compels people to join them. He presents a good narrative, but this is also his weakest area. He's painting with such a broad brush that he misses a lot of important details-- possibly because he's writing at the limits of his knowledge in certain areas. The things he gets right (and his focus on today's problems), more than cover for this. IMHO, this book is in the same league as Hill's, Frankl's and Hoffer's best work, although not at the same level.
I don't necessarily recommend reading the book; I recommend getting it on audio like I did. Peterson is a gifted speaker, and even though he sometimes sounds like he's delivering a talk to a middle school Sunday school class, it still works to get the point across to adults because he's so engaging. I'm glad I own it, and will listen again.
Tell us if you found a gem or a piece of shit, and who peddled it