In this book, Mark Shea presents his reasons for entering the Catholic Church.
This is a fairly small book, but it packs a powerful punch. At the same time, Shea's writing style is always lucid and friendly, and manages to be humorous without making Protestants feel like they're the enemy (as unfortunately too many Catholic Apologetics books do at times). Shea manages to keep things friendly without pulling back from his main and very well constructed argument that Sacred Scripture makes no sense without the support of Sacred Tradition.
I personally know many people who have found the argument the book presents compelling enough to bring them into the Catholic Church, or to solidly buttress questions they had about their Catholic faith. And the number of lengthy, and very defensive reviews here on amazon should give an idea about how agitated it makes some Protestant apologetics with its success. These reviewers wouldn't be so worried about it unless it were in fact making a real impact.
Mark Shea's apologetic is a sort of stealth evangelism directed at evangelicals who have unwarranted prejudices against Catholicism. The author takes the reader on a journey through his own intellectual evolution from a staunch evangelical to an equally staunch Catholic. Shea's journey begins by him attepting to debunk the claims of the Jesus seminar which claims that "orthodoxy" is not the true Christianity seen in the NT, but rather later corrupting traditions added by power hungry clergy. While trying to prove the seminar wrong, Shea realizes his own unthought out reliance on tradition and how Evangelical assumptions are essentailly the same as the Seminar - though perhaps less radical. The question that really gave the author a rough time was the question of the canon. This question enabled the author to see how the seminar people were simply carrying Protestant "sola scriptura" logic to its natural conclusion. The author also realized during his search that many doctrines he took for granted really were not spelled out explicitly in scripture and that he had been relying on tradition. The book is very well written and easy to follow. Shea's style has been compared - rightly I believe, to C.S. Lewis. I witnessed someone close to myself completely change his attitude against Catholicism after reading this book. There is much food for thought here for both Protestants and Catholics.