I was a DBA two years ago. I had about 3 years experience using Oracle. I found this book to be a good review, though I found myself finding various errors. Some errors were typo's, some were just my own disagreement with the author. I also felt like the author didn't have much experience as an Oracle DBA--this may be unjustified, but it was my feeling based on reading his examples and comments. Nonetheless, the sections of the book match up with the overview of knowledge required by the OCP test 1Z0-001 very well, and by design. I just read through the book and took one of the sample tests. Taking the real test, I scored 55/57 (39 is passing), so I think the book significantly helped me prepare.
Another problem with this book is that it is not followed up by others in this series. Now I am ready for the next test, but guess what, no book! That's right, I have the option of buying the book with all five tests, but not one book per test, like this one. I think I'm switching to the "Exam Cram" series due to that (even though I hate the title!)
I hope this helps,
Regards,
David