What you want to make, ideally, is a snuggly spot with good natural lighting during your main reading house and a power point available for when you wish to use electric lighting. So for a reading nook it is best to choose a spot either by a window or within an enclosed veranda or sunroom.
Finally, you will know your nook is successful if you have to battle your pet to actually use it at all. Enjoy the squabbles. Note: these squabbles over ownership will only increase if heating is used during the winter months, whether by fireplace of heater.