Probably the first psychiatric self-help book. Hunter and Macalpine call Mandeville's work "the first book on minor mental maladies `writ by way of Information to Patients' rather than `to teach other Practitioners' . . . [Mandeville] gave a graphic account of his own attack of melancholy when he developed the delusion that he had syphilis" (Hunter & Macalpine, p. 296). Digital facsimile from the Hathi Trust at this link.