Learning Oracle PL/SQL is one of the best books I have read on learning this subject. This book has a little for everyone: you'll learn something if you know the basics of SQL, but have never really done anything with it. You'll also learn something if you've had a lot of experience with Microsoft SQLServer (and T-SQL), but are looking to transition you knowledge to Oracle PL/SQL.
You'll learn about coding anonymous blocks, stored procedures, functions, and packages. You will learn how to write and use cursors, how to organize code into packages, Oracle security basics, Oracle built in packages, and error handling. The book also covers some basics of using SQL*Plus, to make your life a little easier.
If you need a relatively small (less than 400 pages) introduction to Oracle PL/SQL, then this is definitely a book you will want to pick up. If you need more in-depth information after reading this book, pick up the authors' other book Oracle PL/SQL.