Head First PMP helps you understand Project Management concepts clearly. If you do not have any PM experience this book is for you, especially since it explains project management concepts very well. You might find the regular PM books consisting of just theory and it could turn out to be quite dry. Head First PMP, like any other book in the Head First Series makes learning enjoyable.
Yes, if you want to get a sense of what project management is, how it will help on your project, and what kinds of tools and practices project managers use to make sure their projects run well. We also included a lot of scenarios that show the kinds of problems that projects typically run into, so you can see why those tools and practices are useful.
There aren't any prerequisites for Head First PMP. The reason for that is that many project managers have a lot of expertise in one specific area -- like scope management, risk management or procurement -- but have large gaps in other areas. So we couldn't assume any specific knowledge of project management.
Author of Head First Agile, Learning Agile, Beautiful Teams, Head First C#, Head First PMP, and Applied Software Project Management (O'Reilly)