Wes's book is definitely the standard. But I would hold off buying one right now - he's currently working on a (much-needed) second edition, coming out next year (http://wesmckinney.com/).
Joel's book is a great resource for preparing for interviews or learning really basic stuff and less of an introduction to the tools.
Joel's book is a great resource for preparing for interviews or learning really basic stuff and less of an introduction to the tools.