The PMBok is one of the many existing project management (PM) methods. There are many more choices. If you are really new on this subject, I suggest you start out a little smaller. (The PMBok is one HUGE document.) It is important that you understand that project management is just management, so you need to read up on leadership and motivating people. After all, knowing how to handle people is more important than knowing how to draw a Gantt chart. In my opinion, it is easier to start on smaller methods such as Scrum, as they give you a pretty good idea and are not so intimidating.
Regarding certification, being certified doesn't make you a good project manager. It only indicates that you took time to learn the PMBok by heart. It shows potential employers that you took the time and effort to go through dry stuff and take your business serious. So, in respect for job opportunities, it is an advantage.
This was first published in February 2007