I have no idea, as I didn't read the book, but the title to me says it all, that it covers all of AspectJ. The Spring version is called "Spring AOP", which as we know is a subset of AspectJ. And if the book was about Spring AOP alone, I would hope that they would call it "Spring AOP in Action"
I'll let the authors really answer that question. ;)
Since Spring now adopts AspectJ as its programming model (but uses proxies as the underlying implementation technique), the book covers that combination as well. As for the examples, it uses both Spring's proxy-based AOP (with AspectJ programming model) as well as AspectJ's byte code weaving.