Sounds like a predecessor to Big Little Books https://en.wikipedia.org/wiki/Big_Little_Book_series https://en.wikipedia.org/wiki/Big_Little_Book_series which

Sounds like a predecessor to Big Little Books https://en.wikipedia.org/wiki/Big_Little_Book_series https://en.wikipedia.org/wiki/Big_Little_Book_series which only started publishing in the 1930s.