The description of the bed did not provide interior dimensions, i.e. the space the mattress actually has to fit into. So I've got a full bed for a queen mattress. 
I've ordered the larger size, but now I've got a fully assembled bed on my hands. The bed itself seems pretty good. I did order another, after all. It was possible to assemble it alone, but very difficult - the last step, in particular, requires both great dexterity, and reasonable strength.