A Puritan Theology: Doctrine for Life is only outweighed by the reputations of the men whose doctrines are explored in it. As Sinclair Ferguson says in the introductory chapter, "As one returns to the world of twenty-ﬁrst century church, one cannot help feeling that there were giants in the land in those days."
Indeed. If you go to check out the book at Westminster, you'll also find that you can read the introduction, preface, and a sample chapter on union with Christ. Normally, the book sells for $60, but for the next week you can get it for $30. So go and do the right thing.