As most of Boudreaux's posts are in what you define as category (c), the book is not going to change the mind of your liberal friend. Contrast the comments at the bottom of a Cafe Hayek post with those in Marginal Revolution. Cafe Hayek's niche is not opening liberal minds.
This is an interesting point. I think that the substance of the posts selected for the book is often intended to change someone's mind. However, the tone, which echoes the sneering of one of Boudreaux' heroes, H.L. Mencken, has the opposite effect. It works well for those on the same side as the author but probably turns off those who might disagree.
Like Mencken, Boudreaux thinks that politicians deserve to be sneered at, rather than admired, and he wants to encourage readers to adopt such an attitude. However, this can backfire with some of the people that Boudreaux seeks to persuade.