This article uses a computerized style checker—RightWriter® 4.0—to analyze 14 direct-mail letters used to market books to a middle-class female audience. This study outlines methods for correlating stylistic traits with sales success. For this product and audience, letter effectiveness is enhanced by lowering readability levels, as well as by limiting the use of negative words and modifiers. In addition, writers for this audience should avoid words that are too easy or too difficult. However, no correlations emerged between success and letter length, strength of style, sentence length, or percentage of prepositions.