Bonnie’s review nailed it.
The more or less useful 20% of the book can be completely found for free by watching this talk and this talk.
The other 80% is basically just a long infomercial for LinkedIn, and, even worse, is written in an annoying, pseudo-inspirational, fluffy self-helpish style.
It’s not a good representation of what Hoffman (a very interesting and insightful man) has to say at all (you’ll hear way more of that by watching this, this, this, this, etc.), and is therefore a big let-down and a lost occasion. His actual active involvement in the writing process was likely very limited.
For something with substance and written in a normal, digestible way, read The Millennial Game Plan, So Good They Can’t Ignore You, and The Curmudgeon’s Guide to Getting Ahead instead.