Papa Don't Pope evaluates some of the most important issues between Roman Catholics and Protestants, including personal interpretation, apostolic succession, sola Scriptura, and so on. So this little book should be a huge help for anyone (Catholic or Protestant) with honest questions, as well as for anyone looking to interact with the original Protestant vision.
But what's the point in stirring up differences between Geneva and Rome? Don't we have enough division over church and theology already? The truth is, we don't have nearly enough clear disagreement -- because clear disagreement is a necessary step on the way to agreement. So you could say this book has a catholic purpose (even if the future is clearly Protestant). The classical Protestant expression is Soli Deo Gloria. Roman Catholics might prefer Ad Maiorem Dei Gloriam. May God hasten the day when we can say 'amen' to both.