Volume 1 Synopsis: Matthew and Marilla were hoping to take in a boy from the orphanage — but the child brought to them by mistake is a skinny little girl named Anne. She hates being called a redhead and has an extraordinarily vivid imagination. This is the story of Anne's growth through one breathless adventure after another.
This is an abridged version of Heidi by Johanna Spyri translated into Japanese for kids. It's short (about 150 pages), the font size is gigantic, and almost all kanji have furigana (but as with most children's literature, there is not as much kanji as one might wish, so parsing long strings of hiragana can get a little tiresome).
I liked this book well enough and found it easy to read, but unless you already know and like Heidi (either through the original book or the classic anime), I wouldn't necessarily recommend it above any other book at this level — the story's a little saccharine.
There's a surprising amount of world literature available translated into Japanese for kids, so if you like and are familiar with classic books like these, you may find them good material for beginner reading starting at upper N4.