Amazon Kindle Layout

­The original Kindle has an off-white plastic casing and an asymmetric, beveled shape, like a closed three-ring binder. It has a rubberized back that makes it easier for users to hold the device. It's 7.5 inches (19 centimeters) long and 5.3 inches (13.5 centimeters) wide. It's only 0.7 inches (1.8 centimeters) thick and weighs a mere 10.3 ounces.

Amazon has changed the design of the Kindle a few times since its introduction. The third-generation device, also known as the Kindle Keyboard, is less angular than the original model. The Keyboard is just as tall as the first Kindle but is less angular a little narrower at 4.8 inches (12.2 centimeters) wide. The WiFi Kindle Keyboard is 0.3 inches (8.6 millimeters) and weighs 8.5 ounces (241 grams). The Kindle DX is the big brother of the series. It's 10.4 inches (26.4 centimeters) long, 7.2 inches (18.3 centimeters) wide and 0.4 inches (9.7 millimeters) thick. It weighs 18.9 ounces (535.8 grams). The 3G models of the Kindle Keyboard and Kindle DX are just a touch thicker and heavier than their WiFi cousins.

In September 2011, Amazon unveiled three new Kindle models with E Ink electronic ink displays and a tablet called the Kindle Fire. The first new Kindle model, which is now the base model for Amazon, uses a five-way controller and doesn't have a keyboard. It's the smallest Kindle yet, measuring in at 6.5 inches (17.3 centimeters) long and 4.5 inches (11.4 centimeters) wide and weighs 6 ounces (170.1 grams). The two new Kindle Touch models -- one a WiFi only and the other a 3G and WiFi device -- have touch-screen interfaces and very few physical controls. They are a little larger than the basic Kindle, measuring at 6.8 inches long and 4.7 inches wide.

The central feature on all the Kindle models, with the exception of the Kindle Fire, is its electronic paper screen. The screens on all Kindle models except the DX and Fire measure 6 inches (15.2 centimeters) along the diagonal and have a resolution of 167 pixels per inch (PPI) [source: Amazon]. The screen can display images in 16 levels of gray. Unlike LCD screens, the Kindle's screen isn't backlit. That means you'll need a reading light if you want to skim a novel in a setting with little ambient light.