Is this a good book to buy?
McGraw-Hill is a well respected publisher. I'd expect the book to be well edited, proof-read, vetted, and written by a proven expert.
Beyond that, if it is "a good book to buy" -- for you --- will depend on if the author's writing style meets your expectations and the way your brain is wired to learn.
The only way to find out is to buy it.
Steven (mr. "PL/SQL obsessed") has indeed written excellent books on PL/SQL.
You should explore his sites, articles on OTN and http://plsqlchallenge.com as well.
Another 'must read' as well is Tom Kyte's ( Ask Tom Home ) Expert Oracle Database Architecture
"Foundation Knowledge to Understand Most Any Other Oracle Database Book – Required Reading for All DBAs and Developers"
You can find (very detailed) reviews here:
(Tom's book is reviewed there as well)