The Book cases need to be a good portion taller I don't know the ceiling height but right now they get swallowed by the fireplace. I would make the firebox wider & longer with a mantel across the length of the fireplace. Another option is to enlarge the firebox with a opening for firewood but make the mantel full length.

I have a couple fun ideas keeping with the theme of your black/natural wood furnitue. The idea of iron and wood together looks great. Go to your local steel yard and pick up a large angle iron... say a 10" flange, something substantial, and pre-drill to anchor to the existing brick. This will become the support for your wood mantel. If you like the rust look plan to seal it otherwise it'll get quite messy. Now you can choose to use a recycled distressed beam, rough sawn lumber, or something a little more refined. Yor choice entirely, but I would try to match the finish of your mantel to that of the furniture desk tops. Now since your fireplace is offset I like the idea of wrapping your mantel around the left side but stopping flush on the right. This makes it more visually interesting. Finally, I like the idea of painting the bottom portion of brick below the mantel black. If you really want to get crazy you could blow additional brick out and install a corner unit fireplace.

Have look at this Mood-board for some fresh Ideas on Texture, color and accessories
Source: #Isenberg Bath http://isenbergdesign.de/