It would be hard to find a hotter current food trend than Buddha bowls. Pinterest has more than a thousand Buddha bowl thumbnails and recipes. In Google Trends during 2017, Buddha bowl searches indexed (versus the entire universe of search terms) at 15 times where they were at the beginning of 2016; indeed, for much of 2017 the search string "Buddha bowls" was indexing at 100, meaning that the search term was in the top 1% of search terms globally--all terms, not just food terms.
Buddha bowls are best seen as either Asian or Asian-inspired ("fusion") one-bowl meals. The concept is loosely based on guidance from Chinese medicine, that a meal should have vegetables, protein, and grain. Although there would be many, many foods that meet this criterion, such as many pizzas or casseroles, Buddha bowls are a spin on the common Asian thick soup, such as a Vietnamese pho or a Chinese hot and sour soup, where there is a high ratio of ingredients to broth and where the ingredients are whole or in large pieces and not blended or pureed.
Both bowl food and one-dish meals are strong-selling categories in the current cookbook market, and Buddha bowls is as strong a subtopic as any in both of those categories. The book will sell to bowl-food enthusiasts, to big-city and college-town hipsters who think Asian fusion is cool, and to health-conscious eaters. Vegans are especially excited about Buddha bowls, but this title includes both meat recipes and vegan recipes. Certainly, the book will sell as well to people who integrate Buddhist practices into their spiritual routines, as well as followers of yoga and other Asian-inspired modalities.