There’s no backlight, however; you can read only by ambient light. Sony would probably argue that this trait makes the Reader even more like a traditional book, but it also means that you can’t read in bed with the lights off, as you can with a laptop or palmtop.

On the other hand, once those microspheres have formed the image of a page, they stay put without consuming any power. Amazingly enough, that means that you don’t have to turn the Reader off, ever. When you’re done for the night, just lay it on your bedside table; the current page remains on the screen without draining any battery power. (According to Sony, one prototype Reader in Japan has been displaying the same page for three years on a single charge.) Every instinct in your body will scream against leaving your gadget turned on all the time, but you’ll get over it.

The only time the Reader uses electricity, in fact, is when you actually turn a page. One charge is good for 7,500 page turns. That’s enough power to get you through “The Da Vinci Code” 16 times (electrical power, anyway). You can recharge the battery either from its power cord or from a computer’s U.S.B. jack.

The Reader can also display digital photos — they look surprisingly good, considering they’re being depicted using only four shades of gray — and play music files (noncopy-protected MP3 or AAC format) through headphones. With a good deal of preparation, you could even read along as the same audio book plays.

There are two ways to load up the Reader. You can copy your texts, photos and music to a memory card (Memory Stick or SD), which goes into a slot on the left side. That’s also how you can expand the Reader’s built-in storage (64 megabytes, enough for 80 books).

The other option is to import files into a somewhat buggy Windows program called Sony Connect. It’s the home base for the Reader in much the way iTunes is the home base for the iPod, although Sony Connect requires you to drag files manually; it doesn’t offer automatic synchronizing with the Reader.