Comfort is King
If you're going to write the next great American novel, then you should be comfortable doing so. Aside from a desk with a nice and comfy chair of your choosing, consider a love seat or "fat" chair that you can spend some time in. A lot of writing is note taking, research and brainstorming, and sometimes it helps to get away from the desk for that kind of thing. And it's our opinion that reading is best done curled up on cushions than sitting straight up at your desk.