JavaScript: The Definitive Guide covers almost everything. If you take the time to read it, you'll know javascript very well. Then get into jQuery (this guide looks good: http://www.rebeccamurphey.com/jqfundamentals).
My personal experience is "Javascript: The Definitive Guide" feels like a tome. It's a big, dry book. It doesn't stimulate my mind and I skimmed through most of it(chapters dedicated to looping syntax et al.).
"Javascript: The Good Parts" worked wonders for me. I understand the language and I use JQuery for dom manipulation. I understand ground-level DOM and can use it when required. Do you think "Javascript: The Definitive Guide" adds something good which "Javascript: The Good Parts" skips? There are many things but I am talking things which make you a better Javascripter.
I learned JavaScript from The Definitive Guide before The Good Parts came out, so maybe my opinion is skewed, but I don't think Good Parts covers enough material to be useful on it's own (Good Parts doesn't cover DOM APIs at all, for example).
