It looks as if a lightweight cover and unobtrusive light might be the best option. I say that as a person who loves the official lighted cover for the Sony PRS-350 and has hunted for that very solution for the Kindle (and lately the Nook).
After using their lights for over a year, I can't recommend mEdge because the eLuminator becomes awkward and annoying over time. Its longish insert tends to shift in the cover, making the light itself move out of position as you tilt your reader; the insert also makes the light heavier and larger than it should be. Additionally, the touch version can be switched on and off inadvertently, which I find particularly annoying in crowded trains and planes.
I used the mEdge Antique Jacket and two kinds of eLuminator with my Kindle Keyboard for quite some time; I've also used the eLuminator with the Platform Jacket for the Kindle 2 with my PRS-950. That case is a perfect fit and I love and highly recommend it for the Sony, but there are more ergonomic solutions for the Nook ST.
The Antique Jacket looks nice, but it's also a bit too bulky. When the Solis went on sale with Octovo's most expensive leather jacket thrown in for $5 (it had been $80), I bought the package and was amazed how much more enjoyable my user experience became. The slender fit and lighter weight still make me feel as if I own a brand new device every time I break it out.
If you choose the right cover and light, you can have that same experience on the Nook ST.
What I'd look for is (1) a slim-fitting elegant cover and (2) an attractive, firmly situated and unobtrusive light like Octovo's Solis for the Kindle. I've heard people praise the
Verso Arc Light in that regard, and seeing it at B&N definitely made me want to pick one up, since it fits the ST.
I'll check my Solis over the weekend to see whether it fits the ST (once my grillfiend opens her present!), but the Arc is designed quite similarly and seems to be used the same way.
The only reason to even consider a Solis would be its looks. If you own a swanky leather cover, the Solis resembles a silver cap at the top, which makes it look like you're carrying a flask of expensive Scotch or perfume (depending on the style of the leather). I'll let you know whether it works and, if so, how well.