J. R. R. Tolkien
The Hobbit is a book about greed.
The underlying premise is about heirs of a stolen fortune going on a quest to win back their fortune from a dragon (who are known as a species for their greed).
There are several unflattering passages about the greed of dwarves throughout the book, something that Tolkien changed in later books. This is seen most emphatically when Thorin refuses to compensate the people of Laketown forcing Bilbo to take action.
There’s an air of greed surrounding the ring. From Gollum’s and Bilbo’s insistence that it was a gift, when each stole it. To their lust for it, calling it their precious. It also represents the ability to own anything, as Bilbo survives away from the dwarves living up to his title “burglar” by leveraging the invisibility to steal what he needs to survive.
Bilbo is the counter-theme to greed. He is happy with what he has, for the most part. He has simple desires, yet accomplishes more than anyone else. One thing I noticed, this time reading the book, was that from the point that Gandalf leaves Bilbo saves the Dwarves every single time. One of the flaws in the movies is that it doesn’t follow that.
Bilbo isn’t without aspiration. It’s just a different aspiration. While Thorin is so set on wealth that he refuses to invest in the infrastructure that would foster more wealth for all, aka Laketown, Bilbo wants adventure and a full stomach, and ends up being the first to explore the treasure under the mounting and finds the Arkenstone.
I think that is one main difference between greed and ambition.