Which on is OK?

From a book

Something fell out of its pages.
Something fell out from among its pages.

Question

Which on is OK?

From a book

Something fell out of its pages.
Something fell out from among its pages.

Answer

Both are fine. You can also say

"Something fell out (or 'tumbled out') of (or 'from') the book."

"Something fell out from amongst the pages" (sounds old fashioned, but I like it).

Answer

I would suggest:

Something fell out from between the pages.

Answer

Which "one" is OK
Either is fine. The 2nd one is more formal/more old English