Another cool feature of the NCL solos cabins (at least on the Bliss - I'm not sure about the other ships), is that they have virtual windows similar to Disney's virtual portholes. They also have a coordinator who arranges meet ups, dinners and activities for the singles if you so desire.
I found a video of several different types of cabins on the Bliss. The studios start about 2:08.
They are definitely small, but they'd get the job done (assuming you're not claustrophobic). They are really popular and often sell out quickly.