Question about KING YAO'S book

Hi i was wondering if anybody have brought a copy of king yao's book "weighting the odds in hold'em poker". I'm really interested in purchasing this book but want some opinions about it before I decide to buy it. In addition I'm thinking about purchasing the following 3 books but is wondering which ones are rated higher then the others.

King Yao- weighting the odds in hold'em poker

Bob ciaffone- Improve your poker

Matt Matros- The Making Of A Poker Player: How An Ivy League Math Geek Learned To Play Championship Poker

Thanks for the advice and help