Thank you everyone for all the great feedback, and wonderful to know there are lots of people reading along or planning to do so in the future!
Nice idea about mentioning the grammar level in the first post on the main thread @polenep. I’m just afraid that it might, like you say, look like a requirement and put people off. My own grammar is way below N5 (I took the N5 test a few weeks back so will find out exactly how much below petty soon!) but with the help of the thread and all the other resources available (Jisho, Hi-native, etc) I’ve been able to follow along so far - and learn a lot!
@ShawnPCooke did a marvelous statistical analysis of the level of kanji in the book, an amazing bit of work if you haven’t seen it yet. Perhaps something similar could be done with the grammar? I’ve no idea. But then we’d be on safer ground when saying just exactly what level the book is at.