In this book Edward Reilly provides the essential documents connected with the friendship between the eminent Viennese music-historian Guido Adler and the composer Gustav Mahler. The nature and extent of that friendship has been the source of a number of questions for some years. Although Adler was the author of one of the important early studies of Mahler, he was reticent about speaking of his personal connection with the composer, and for many years the single available published letter from Mahler to Adler was one that was sharply critical in tone. A few somewhat disparaging references in Alma Mahler's recollections also raised questions about the degree of friendship between the two men.