A prerequisite to that book is understanding objects and pointers. With that I mean how they are represented in actual memory. We don't have to deal with those details when using HLLs. E.g the book talks a lot about "slots" but it is useless unless you understand how a slot and how a reference to a slot is implemented.
Therefore firm knowledge of C is required. Then when you have that knowledge, you can build an object model. I suggest starting with just two simple types: array and integer objects.
Then you can implement simple memory management. The easiest is probably to begin with reference counting. After you have that, continue with mark and sweep, copying collection and more advanced techniques.
