Book quality and a historian's willingness to recommend it

What does an author's personal conduct, apart from plagiarism, have to do with a book's quality?

A book's quality and the personal choice to recommend its author are separate judgments.

Clarke separates the quality of a book from his personal willingness to recommend its author. A work can contain useful history even when he does not want to promote it. His distinction concerns giving an author publicity and sales, rather than treating personal conduct as a measure of every claim in a book.