Clarke Ching is an expert in the application of Agile and Theory of Constraints.
He wrote the (surprisingly readable and listenable) business novel, Rolling Rocks Downhill. It's an engrossing story about a large software development team which discovers the underlying principles of Agile (and commercial software development) all by themselves. It's a bit odd for an Agile book because (a) it never mentions the word Agile (b) it doesn't preach at you and (c) it helps you understand the strategic/business benefits of agile, not just the mechanics. If you're looking for a book that tells you how to run a stand up or which colour stickies to use, this ain't it. You can buy the kindle, paper, or audible version from Amazon. If you're keen you might also find them on iBooks.
Now, if you've got a spare twenty minutes up your sleeve you could read Clarke's first book, Rocks Into Gold, for free. It's a parable which explains the underlying mechanics and commercial aspects of Agile. If you're of a particularly technical disposition and you don't like "biz speak" then you might not enjoy it and you'd be far better off spending those 20 minutes on Facebook. That said, if you do read it and then, if you're still keen, you could do far worse than listen to (or read) Clarke's hour-long interview with Eli Goldratt.
Oh, and, if you look in the menu above, you'll find a link to a new book. It's due to be published on the20th of January, 2017.