I don't think it's all saturation. To be honest, since I got my EVO3D phone with a 4.25" qHD display, it's fairly rare I use my Nook anymore.
The phone is easier to hold, always with me, has great resolution and contrast, and is big enough (barely) to comfortably read on for fair amounts of time. This kind of device simply wasn't available a few year ago. Is it as good as the eink Nook for reading? In some cases, like reading at night, yes, but generally no. But it is good enough.