Schwaber’s first book, Agile Software Development with Scrum, is more of a reference book than a how-to. It describes what Scrum is, but not so much the nuances of how to use it. The second book includes a reference section in the back that pretty much recaps the first book. So, start there. If a pass through the reference section makes sense to you, then proceed directly with the second book. Otherwise, pick up the first book as well and use it to get up to speed.

If you are not yet up to speed on XP, the quintessential tome, Extreme Programming Explained: Embrace Change (2nd Edition) by Kent Beck, is still the best starting place. I’d recommend reading that before reading up on Scrum. As you do, just keep in mind that Scrum essentially replaces and expands upon the XP “planning game.” Don’t skip reading about the planning game. Just understand that if you have questions about how the planning game works in the real world, hold those questions until you get to Scrum.