Ignore all his complaints about MBA/Ivy league programs and how they teach negotiations. A lot of what he accuses them of are not true - he mostly sets up strawmen arguments against them. The majority of his book is in alignment with what those other books/programs teach, including many of the cases where he claims otherwise.

Consider his rationale for criticizing other books so much. He could have simply written his own book on negotiation without spending so many pages throughout the book complaining about other books. Why does he do this? He's playing psychological/marketing games with the reader. Similar to the dialogue in Thank You For Smoking:

Joey (the son): so what happens when you're wrong?

Nick: OK, let's say that you're defending chocolate, and I'm defending vanilla. Now if I were to say to you: 'Vanilla is the best flavour ice-cream', you'd say...

Joey: No, chocolate is.

(dialogue goes on for a while)

Joey: ...but you didn't prove that vanilla was the best...

Nick: I didn't have to. I proved that you're wrong, and if you're wrong I'm right.

Chris Voss seems to be playing that game: He's trying to elevate his book by claiming other books are wrong.

The other thing about the book: It works well in a somewhat narrow scope. In particular, some of the advice in the book will damage relationships. This isn't surprising, given his whole negotiation career involved scenarios where he would not have a continuing relationship with his counterpart on the other side.

As an example, his tip on "But how do I do this?" My last manager was very skilled in getting her way with this approach. Within a year of her becoming the manager 3 people had left the team. Sure the tactic works initially, but people will wise up to it if you use it often, and they resent the mind games involved.

A good negotiations book will differentiate between strategies where the relationship is important vs one where it isn't.

Not to deter you from reading the book. It does have some pretty good advice I've not found in other books. And it definitely is more practical than other ones. Just do not stop after reading it.