When discussing profitability, genre fiction has been leading the way all along, with romance, mystery/thriller, and fantasy among the genres with top-selling novels year after year. Genre fiction makes up most of the sales volume for books globally, with romance having the largest market share due to its loyal following and constant demand in various formats, including ebook, paperback, and audiobook formats. Self-help and personal development are other profitable categories, particularly when related to current hot issues such as health and wellbeing, productivity, and finance. Non-fiction genres including true crime and memoirs have become increasingly popular as well, even expanding beyond the book format into podcasts and documentaries. Of course, genre isn't the only factor that affects profitability, which is also influenced by marketing, cover design, and publication methods. Most contemporary writers prefer online book publishing services to get their works published widely.