O'Reilly's JavaScript: The Definitive Guide, ISBN: 1565923928 . Very comprehensive book on the JavaScript programming language.
Yet another book from O'Reilly with a random animal on the cover; this one a Rhino.
Note--the RhinoInterpreter for JavaScript that comes with MozillaBrowser is (reportedly) named after the cover of this book; not the other way around.
Version 4 is a nearly-complete rewrite from version 3 I hear.