This appears to be the omnibus of all three HARMONIOUS releases, the first of which was initially released on CD before being published in this book. HARMONIOUS: https://www.doujinshi.org/book/66467/HARMONIOUS/ HARMONIOUS 2: https://www.doujinshi.org/book/57866/HARMONIOUS-2/ HARMONIOUS 3: https://www.doujinshi.org/book/12067/HARMONIOUS-3/
This release has additional pages, is of much higher resolution, and has better color. However the two-page spreads have been scanned and cropped in a way that arguably makes the previous releases superior for those pages.