Is your goal to learn the virtual machine instructions that power a Prolog implementation or to understand Prolog?
When I learned Java I also took a similar route to understand the JVM and while it was nice to know the only practical piece of information I learned from months of work was that the JVM did not implement tail recursion, they may have done it since.
The other thing about learning Prolog is that there is text book Prolog code and real world Prolog code. The only book that actually helped with real world Prolog coding was The Craft of Prolog by Richard A O`Keefe (WorldCat)
Also see:
You might find the history section of value.