Translation:They wrote a short story, and then a book.
Why is "they wrote a story and later a book" wrong. Later is marked read for a reason.
The new voice pronounces потом as "patAm" when in the sentence, and as "pOtam" alone. The correct pronunciation is "patOm".
Does Russian use 3rd person plural to discuss an individual (that's already been established in context) like English does?
This sentence reads like it's one person in English.