I wouldn't specifically read a book just to put it into a personal statement, if you were reading one already and wanted to reference it then great. I wouldn't say it gives any advantage to your application or that this guy you've seen has the perfect recipe for personal statements.
If you've genuinely read a book and enjoyed it and can talk about it then feel free to mention it but IMO it's not really necessary, I have friends at Oxford who didn't mention books on further reading. Furthermore, I have friends who DID and got questioned about it quite a bit.
I wrote my personal statement how I wanted to, including what was important to me and conveyed things about me, I mentioned an article that interested me regarding the use of xenon gas in treatment of cerebral hypoxia of the newborn - making it clear that this interested me, HOWEVER, not implying I fully understood all the pharmacological and physiological mechanisms occurring.