The Pirc is a modern chess opening whose unbalanced nature usually leads to eventful play and a decisive outcome. A perfect complement to John Nunn's earlier work, The Complete Pirc, a guide to pawn structures and their importance in forming and executing plans.
John Denis Martin Nunn is an English chess grandmaster, a three-time world champion in chess problem solving, a chess writer and publisher, and a mathematician. He is one of England's strongest chess players and once was in the world's top ten.
I play the Pirc/Modern regularly on ICC, and use this book as my primary reference. It's still quite reliable - Pirc theory doesn't move that quickly, which is why I play it. Like all the Nunn books, this one is very nicely written and laid out.