Hi, actually I just started to use it. By now I can only say it is a good practice for me from a “reading” point of view, thanks a lot for your help. It is not easy to find this kind of material for starting with japanese language.
From my point of view this one is way more begginer friendly than kids books since even they are wholly in hiragana (almost) those books uses words you won't see in daily life or in your studying textbooks, despite having done minna no nihongo 1 and 2 and anki decks for a long time now, I totally found it to be super useful.
A series like this way, gradually increasing difficulty, is what I initially looked for, so glad you did.
I'd definitely recommend this set to people who wants to start reading normal Japanese and not words like "little prince" or using おる.
This should be the first reader for beginners who already know hiragana and some basic Japanese grammar and vocabulary. The first chapters are very easy to understand. Later on the level rises but for beginners it's still okay (I guess).
I also like it that the chapters start with the Japanese text before splitting it up sentence by sentence, so there's less temptation to cheat. Please keep this in your next readers as well.
One thing that irritates me is the lecture at the beginnging of each chapter not to look for the roumaji before reading the Japanese text. Here I think, once is enough. Also it might be a good idea not to repeat the the furigana on and on for already introduced kanji, e.g. after chapter 2, you should know how to read 私, so the furigana could be left out. That goes especially for single kanji. Just an idea for future revisions.
All in one it's a great reader.