I really like how he structured it - the first chapter has some basic vowels and consonants, which means we start building some simple words right away, and each chapter introduces a new set with some new complexity. I had started with Radice's book, which I think is great for a deep dive/focus in writing and understanding the Bengali abugida, as that's what all of the first unit (~13 chapters) is focused on. Since posting that, I've also acquired the two books that u/Kalpanita mentioned in that thread by Hanne-Ruth Thompson: both her full 800+ page grammar and the Beginner's Bengali textbook. I listed out several books last year in this thread. I dont know if it's bad/ineffective necessarily, I just don't recognize the book from your description, which is why I'm again asking - what book is it?