Here are my top picks for books that will give you the edge on your Oracle certification exams.
1. OCP: Oracle8i DBA Certification Kit
By Chip Dawes, Joe Johnson, & Matthew Weishan. "Expert coverage of all five Oracle DBA exams -- brought together in three authoritative books and three CD-ROMs packed with exams and practice tools!" -B&N Editors
2. Oracle OCP Oracle9i Database: Performance Tuning Exam Guide
By Charles A. Pack. This study tool covers all official exam objectives and contains chapter self-tests, two minute drills, a glossary of key Oracle terms, and over 300 practice questions.3. ) OCP Oracle9i DBA Certification
By Jason S. Couchman, Charles Pack, Daniel K. Benjamin, Rama Velpuri, & Sudheer Marisetti. This set includes four books, each covering an exam. According to the publisher, "you'll find in-depth details on all the material covered on these challenging exams, followed by practice questions and chapter summaries. Books and CD-ROMs combined contain 1,200+ practice exam questions."4. OCP Oracle9i Database: New Features for Administrators Exam Guide
By Daniel Benjamin. From Oracle Press, this book will guide you through the official OCP exam objectives and provides practice questions and chapter summaries. The CD also provides hundreds of practice questions.5. Expert One-on-One Oracle
From a well-known Oracle expert, Thomas Kyte, comes this book on everything Oracle. Although it is not specifically for certification, the editors over at Amazon.com rave that this is "the best book about Oracle products ever put out, this book is a model of all aspects of technical publishing: scope, level of detail, clarity of explanations, and quality of examples".