I got an eReader as I have arthritic hands and find holding a book painful; it has revolutionised reading time for me.
This cover is excellent if I want to read in bed whilst my husband sleeps; but it does make the Reader considerably heavier to hold, and bigger, too.
Negatives:- If you're not using the light, it's a bit clumsy and awkward; you can't fold the light to the back of the Reader like you can with the other covers, and neither can you easily read the Reader through the unlit screen as it distorts the screen slightly (for some reason this is not nearly so apparent when it's lit up). So the screen has to sit to the left of the Reader if you're not using it; and this usually means two hands required!
You also need to be careful not to let the lightt-screen 'slap' against the Reader when you close the case, or you can permanently mark the Reader's screen.
It's not a 'blazing' light; it doesn't do a lot if the light in the room is just a little bit dim, it's more for reading in darkness.
Positives:- The usual 'mini-torch' style booklights don't work with a Reader; they simply reflect off the screen. This DOES!
The light only lights up the screen - not the entire room, and this means you can use it when your partner is trying to sleep without disturbing them. It's very handy to have it all-in-one - no extra 'bits' to carry around or lose. The batteries seem to last a long time, and replacements can be bought pretty-much anywhere (no searching for those difficult-to-find 'watch' style batteries)
To sum up; if you read at night while your partner sleeps, or on an aircraft at night, buy it. Other than that, don't bother!