Over the last 2.5 years, David Gertler has helped me edit a book I am writing about chess. As a philosophy professor, I have had 12 books published in the last decade (mostly new editions of textbooks), and so I have extensive experience with editors, proofreaders, compositors, and so on. Mr. Gertler's work has been exemplary -- helpful, insightful, and prompt. He has done research for me, improved my prose, and noticed apostrophes that were backwards. He has marked up around 35 different chapters (sometimes multiple drafts), totaling several hundred single-spaced pages. I have agreed with upwards of 90% of his suggestions, which might be a record in my experience. He is one of the very best.