In Nicholas J Brown's book, The New Penguin Russian Course, in chapter 27, I see the sentence,
In all the books written by this author before 1939 there are interesting women.
Во всех книгах, написанных (prep. pl.) этим (instr. sing. m.) автором (instr. sing. m.) до 39-го года, есть интересные женщины.
Only the "(prep. pl.)" was provided by the book, but this is the case I don't understand. Plural because what was written were books.
But why prepositional?
Instrumental would denote who wrote them, i.e. 'with' or 'by' so the last part of the sentence makes sense.
Contrast this with the sentence,
In our shops it is difficult to find books written by modern Russian writers.
В наших магазинах трудно найти книги, написанные современными российскими писателями.
It seems that both participles share the same role, yet this one is also not instrumental....?