How much Hadoop knowledge should one have before diving into Pig?

I've spent maybe 2 hours looking into Apache Hadoop, so just basically familiar with the high level terms.
Should I spend more time working on Hadoop before diving into Pig? Does the Programming Pig book give a good overview of Hadoop in general?

Looking to broaden my knowledge in an area where I don't have very much.

Learning Pig will involve learning Hadoop. But I wrote the book with the assumption that readers were not necessarily Hadoop veterans. I explain Hadoop concepts as you encounter them in Pig, and an appendix walks through the basics of Hadoop.

Alan.