"Marcus and Corinna read the books."
Translation:Marcus et Corinna libros legunt.
It would mean either ‘of book’ or being a second subject of the sentence, as per the other comment. The meaning then would be ‘The book’s Marcus and Corinna are reading’ or ‘Marcus and Corinna [and] books are reading … [what]’.
Edit: I forgot to mention that it could also be vocative plural, so something along the lines of ‘Marcus and Corinna—O books!—are reading’. Quite Shakespearean.
I don't want to spend too much space getting off-topic, but thank you! I love dramatic music in general, which is probably why the Doctor Who theme in all of its variations is my favorite TV theme music of all time. Honestly not sure if also being a fan of the show is biasing me in that direction, but :-)
In this class, we'll be talking about Corinna, and she would appreciate it if you spelled her name correctly.
The course contributors need to manually enter all of the different answers to each sentence individually. This is a large enough task as it is. Add to it the way Latin declines all nouns, including names, and yes, the course contributors have drawn the line and will not be accepting alternate spellings for Corinna, Livia, Stephanus, or Marcus.