I'm a little late on this one, but here comes - hope you are sitting down.
It looks like a bookcase.
Ah, you say - it is a bookcase! Yes, but it doesn't have to LOOK like a bookcase. It's a bit stark for my taste. Here's what I would do to fix it:
1) As Paul and Jim said, make it match the room. You have plenty of room, so use the same width stiles as your fireplace stiles. Use the same plinths too. It you think that's too wide, cut it back an inch. Anything narrower is too narrow for that size case on that sized wall. You could flute them (or reed them - whatever the profile) too. Probably a stock trim piece at your local moulding supplier.
2) Drop the top. The upper rail is too thin. Make it wider and you can trim it with a taller piece of moulding that doesn't look like it's a cheap home center solution.
3) Make the top of the fixed shelf @ 30", 36" or 42". These are the very common "counter" heights.
4) Raise the bottom shelf. Lowering the top rail, and raising the lower rail will give the piece more elangance and mass. Maybe an inch in both directions.
5) Give the piece depth. How so? This way. Make your left and right stile, and upper and lower rails, the frontmost pieces. Drop the shelves back 3/4". Apply the base moulding in front of the lower rail.
6) You can, if you want, paint the inside back of the case the same color as your walls. That way, you cut down on the amount of stark white.
Todd