I happened on this small free standing writing space in ivillage. A friend of mine has something similar for her metalsmithing shop. She started with a prefab storage shed, such as the ones you find at the local big box hardware stores and then paid a contractor to finish the inside with drywall and lay in a hardwood floor. It has the same small porch where she has a chair, a few catus plants and a string of chile pepper lights that illuminate the eves in the evening. A small a/c unit keeps the place cool and she had an electric line run to it from her home. It is quite spaceous and charming.
This backyard turquoise painted writing space has everything that a writer could need to work. A cozy desk, a comfortable chair and space for all the research materials you would need. Many famous authors choose to build small writing huts for their work, including authors like Mark Twain, Neil Gaiman and others. The fact that you need to walk that couple of yards into your backyard seems to help their minds switch into work mode and the isolation you gain from distractions can be beneficial.
Would you like this writing space for Christmas? I think that I would.