Of course it depends on your background knowledge and your intelligence, but for someone who knows the basic novice concepts of java already and who should have an ability to learn computer science at university level, it's enough.
... Is this book is to know basic concepts in Java? Is this book enough to take SCJP exam?
I would say, you have started with an excellent and correct book for covering the basics of Java to take up the certification.
But just going through that book alone IS NOT ENOUGH to take up the exam. Thats why there is an another book dedicated for that.
You just get the basic and core OO principles (Inheritance, Polymorphism) and an introduction to important concepts like Threads, Collections, Arrays etc from Head First Java. It would suffice for you then to proceed with the Certification book.
Good luck. [ August 18, 2007: Message edited by: Raghavan Muthu ]