The layout of Evernote is both art and science. We might use a metaphor to help explain how cool it is. Notebooks are large filing cabinets that can contain folders of text, photos, etc. The ‘folders’ are where I would store pieces of each chapter, research, quotes, interviews and so on. I had one Notebook for each chapter, and others for larger containers worthy of a notebook but not a chapter outright.
I store my research in Evernote. I also write draft material there, but I've never considered writing an entire book in Evernote.
It makes sense. (But I prefer Scrivener.)