I read the first 30-40 pages or so and the HLA stuff is pretty simple. Some of the book lacks explanation but can be googled, it brings up things like the EFLAGS register and then doesnt tell you what it is or what it does.
I wasnt sure if this was worth learning though. What is the difference, performance wise, between HLA and pure assembly?
Here is a link to the site I downloaded it from
http://webster.cs.ucr.edu/AoA/Windows/index.html