1) It's self contained. No dependencies on third party OO libraries or frameworks.
2) The code is very readable.
3) It's a canvas library, so it's fun to work with if you're into graphics and visualizations.
4) You'll learn a lot about how many JS projects are built, documented, and tested, if you get it to build and the tests running on node.js.
Here is what I would do:
1) Check out the project and get it building.
2) Read all the files in the util folder. You'll see a lot of methods added to Object and Array.
4) Then take a look at the base class: https://github.com/kangax/fabric.js/blob/master/src/object.c... and an inherited class: https://github.com/kangax/fabric.js/blob/master/src/line.cla...
5) Search for instances of the "bind" method, and see how they're used.
Finally, this is just a personal opinion, but I don't like Crokford's chapter on OO JS. I just don't think it presents your options well. If you decide to write a large project in JS using OO techniques, I think you'd be better off utilizing an OO library, compiler, or framework like TypeScript, Google Closure, Prototype or CoffeeScript, than you would charging forward armed with Crokford's chapter on OO.