Just finished reading OCA Oracle Database 11g: SQL Fundamentals I: A Real World Certification Guide - Packt Publishing.
What i liked: the book is accessible to anyone; the examples and their screen casts make easy to see what exactly the author is talking about. Each chapter has a "Certification objectives covered" and a "Test Your Knowledge" sections which are helpful, something you'd expect from a certification guide. The book also covers (very slightly, though) how to use SQL with programming languages including PL/SQL, Perl, Python, and Java; but why is Ruby not covered (-:?
Bonus: introduction to APEX.