From the start of 星の王子さま:
It was when I was six years old. I saw an amazing picture in a book called "Stories that Really Happened" that (someone) wrote about the primeval forest.
I'm a bit confused about 書いた here. I would have expected this to be in the passive form. Since it is not, there must be some implied subject of the verb, but these are the first two sentences of the book so the only subject I can imply is "someone".
Is this usual in Japanese? Would 原生林のことを書かれた本 be more, or less natural, or equally acceptable, and why?
I read this question but I don't think the answer is applicable in this case.
I've just realised I'm even more confused, because in my interpretation 本 would have been the object of 書く before it was made into a relative clause. But after making it a relative clause 書く is now taking a second object: 原生林のこと. So if 原生林のこと is the object then wouldn't 本 have to be the subject, so I would get "a book that wrote about the primeval forest". But books don't write things. People write things in books.
In the active sentence I guess I would have said something like 原生林について本を書いた. So perhaps my alternative should have been 原生林について書かれた本.