Reddit mentions of WordPress: The Missing Manual (Missing Manuals)

As already suggested, the Codex is the resource from the source. I'm in the midst of my first WordPress site development and I've found Matthew MacDonald's WordPress: The Missing Manual from O'Reilly Media to be a very well done book that lays out the broad overview you seek. It includes pointers to websites with all the examples in the book and links to every tool and plug-in mentioned within. It's a quick read, especially if you're already familiar with the dashboard UI, and it seems to raise all the fundamental design and content issues one should best consider before getting deep into development.