Last month I ordered some readers from White Rabbit, which finally arrived today. I think the one I’m most interested in is 「なぜ？どうして？みぢかなぎもん（１年生）」since it addresses cultural things about Japan like, “Why do you say もしもし when you answer the phone?” and also more generalized things like why are stoplights red/yellow/green. Which were the two I read tonight, though honestly I didn’t quite follow the entire explanation of the stoplights.
The other two books I got were 10分で読めるお話 and イッキによめる！ the latter of which has some reading comprehension questions (and answers) which is interesting. I didn’t really make it through a story in that one yet, though. I may wait to read this one last, since it seems slightly more advanced than the other two (or at least I lack the vocab for it still).
10分で読めるお話 (at least for the first grade level) seems to be kind of Level 3 絵本, I’d say? Not enough that you could get the whole story from the pictures, but enough to help you along if you’re stuck with the basic idea. It’s interesting reading this one after all the Level 2 JGRs which are theoretically about the same level of picture book. It’s definitely more written for a native Japanese child, with kind of a simplistic idea, but it’s oddly harder to read for me than the JGRs were. I think part of it is that the first story has a lot of dialog that was written as if it was a parent/child talking, which is kind of different, grammatically and in vocabulary, from the focus of student/teacher or colleagues at work that my textbooks tend to take.