O'Reilly has a book on JDBC that I hear is pretty good. However JDBC isn't that deep of a subject in and of itself. You can probably find sufficient JDBC info in many
Java books, as well as on the Sun site. If you are a novice to the world of relational databases, and you are using Oracle, the book
Oracle 8 Programming: a Primer (Rajshekhar Sunderraman, Addison Wesley) is very useful, giving you some good theoretical as well as practical info on relational databases and Oracle, including JDBC. If you are already comfortable with relational databases,
Oracle 8i Application Programming with Java, PL/SQL and XML (Wrox) has a lot of good info.