John Resig is the lead developer on the jQuery team. This book is not about jQuery, though if you work your way through it, you’ll be well equipped to understand the jQuery source code.
It’s a good book and I learned a great deal from it. It’s not as good a book as it could have been. The editing is sloppy and there are too many typos. Resig fails to follow Strunk’s dictum, omit needless words: the writing is clumsy and wordy. Inline <code> should be typeset in a distinct font in a programming book. Finally, no one should talk about consuming JSON without mentioning browser security.