The best cover I've found for eReaders is the ones made by m-edge; they also have the best book light in the sense it lights the entire screen and can be positioned so it doesn't cover up the screen. There are two approaches.
One is the Executive cover which has the light inside the cover at all times.
http://www.medgestore.com/products/n...p?device=nook3
The second option is the m-edge Go Jacket.
http://www.medgestore.com/products/nook3-go.psp
With the Go Jacket the light is carried separately from the cover and inserted into the cover when you need a book light. The advantage of the Go Jackets is lighter weight. I've used both but I only need a book light at night while I carry my Nook around all day so light weight together with a very sturdy cover works best for me. Unfortunately there are just three colors right now.
The cover and the light are two separate purchases. The light is called the m-edge eLuminator. It fits most of the m-edge products.