Carpe Librum has reopened, at 2134 L St. NW and at Union Station. I visited the first of these location today. Whether through lack of space and shelves, through having to share with Union Station, or both, the stock is considerably smaller than it was at 17th St: it might be a sixth or eighth of what it was there. Still, anyone who really needed to spend money could have found something to buy. I bought a copy of the JQuery Cookbook, not to spend money but for quick reference when, as sometimes happens, I need to write or adjust a bit of JQuery.
According to the cashier, the L St. location will be open until July.