I, too, am surprised that Java Concurrency in Practice is missing. Rich has mentioned several times. Odd.

As for the Ruby influence, Rich mentioned that he is a "language nerd" and learns all kinds of languages. Whether any one language shows up in some way in Clojure is another matter ;-) I think the Ruby influence shows up in Clojure's ease of scripting Java, cutting through the ceremony to get things done in minimal code.