This book is absolutely superb. It is a powerful and hard to refute defense of dialetheism, the view there are true contradictions. This is an affront to the western world's sensibilities, and it is a welcome one. As Priest points out, consistency has enjoyed a free pass since Aristotle. It turns out, the arguments provided for it are weak. Either our views of consistency truly need to be whipped into shape, or there is much more to logic and rationality than is dreamt of in our philosophy.
Whether you approach this book as wrong from the beginning, or as right, it is well worth your time. If you are against the views, then digest what Priest has to say and figure out what is wrong. Don't hand wave it. Defend your position. If you are for the views, then digest what Priest has to say, and prepare to defend yourself. This is not something that shall enter philosophical circles lightly. It is a conversation that needs to happen, and deserves to happen. This book is the beginning of that conversation.
You may be thinking to yourself, "Oh these are just some silly philosophers talking about silly things." To those of you out there who approach this with an incredulous stare, take heed of the power of non-trivial inconsistent systems. Semantic closure becomes a real possibility. I only need to point at the expressive power of English to tantalize your imagination. (The semantic inconsistency of English gives it its power. Truly, it is really hard to come up with a well-formed sentence in English that is absolutely deductively senseless.) Further, paraconsistent mathematics is a delight. Priest treats paraconsistent set theory and arithmetic in chapters 17 and 18. As an undergraduate mathematician, the beauty and elegance of the systems was shocking and intriguing.
Priest's excellent writing, professionalism, and scholarly commitment makes this a joy to read. He is not afraid to admit when he has been wrong. (Indeed the second edition includes autocommentary on the first edition, marking where has erred in the past.) This is the mark of a truly great thinker, who wishes to find the truth, not just defend his version of it. When Priest is marked down in the annals of great philosophers, this book will be by his name. It will challenge you to think, and to quote Kant, it will "awake you from your dogmatic slumber."