Say I have two authors that each wrote a book (not together) and I want to refer to both of them in one sentence while lumping their books into one noun, should I put an apostrophe right after the second author?
You should make them both possessive if they do not share ownership of the books.
I read Stephen King's and J.K. Rowling's books.
If they wrote books together then you would only pluralise the last in the list.
It all comes down to ownership, or co-ownership. If they are co-owners, or co-authors, then they are grouped together and are made possesive as a group noun, for example:
- I'm at my mum and dad's house. (they own the house together, so one is possessive)
- I've been to John's and David's houses (two different houses, so both are made possessive)
As an alternative to your example, you could also write:
I read the books of [author 1] and [author 2].
This example doesn't need possessive nouns.