If last year’s runaway success of Amazon.com’s Kindle e-book reader didn’t surprise anyone, how about this year’s continuing momentum? The $359 Kindle is out of stock again, and it won’t be back in time to fill anyone’s stockings this holiday season. For technology and gadget lovers, the black and white, single-purpose Kindle is an anomaly. It doesn’t play games, doesn’t show movies or TV shows, and it doesn’t even have an app store. It’s for one thing: reading electronic text.