So, with this in mind, more and more of us will be 'reading' books online. Amazon's Kindle only does reading, so is it fair to compare it to iPad? We don't care. We're going to compare it anyway.

Readability
Can you look at it for a long time without eyestrain? Are the characters on the screen crisp and easy to see?The Kindle uses a reflective screen with no backlighting β€” just like a paper book β€” while the iPad has an LED backlit display. Each has advantages and disadvantages. The Kindle requires decent external lighting; you can't read well in a dark room. The iPad has a bright screen, but it doesn't do well in direct sunlight.

Some have no problems reading a backlit screen, but it bothers a lot of people. However, reading for long periods on an iPad is difficult. But most don't have a problem spending hours with the Kindle. As first noted by John Gruber on his Daring Fireball blog, the reason may have to do with how close together the pixels are, a factor known as pixel density. The iPad's pixel density is less than that of the Kindle β€” or the iPhone β€” so the characters are less distinct. The advantage here goes to the Kindle.

Size
Is it easy to handle and use? Are buttons and other controls comfortable to access? Does using it create physical strain?

At 1.5 pounds, the iPad is relatively heavy, compared with the Kindle and iPhone.

The iPad has an advantage when it comes to page turning β€” it's simpler and natural. You can either just tap the edges of the virtual pages on the screen in the iBooks app, or move your finger along the bottom as though you are turning a page. It works this way in the Kindle app, as well. The Kindle 2 requires that you press long buttons on either side of its case to turn pages.

Book Buying
Can you buy books directly from the device? Are you able to read purchases on other devices?

Both the Kindle and the iPad have dedicated e-book stores accessible from within the respective devices. You can buy books separately, too β€” from Amazon's Web site for the Kindle, and from iTunes for the iPad. Unfortunately, you can't buy books directly from within the Kindle app on the iPad β€” you must use the iPad's Safari Web browser, where you can complete your purchase.

Price
The iPad costs a minimum of $499, though you can pay as much $829 for a fully loaded model. And if you get one that connects to AT&T's 3G wireless network, you'll pay service charges for that as well.