I don't think I ever saw this in print until today. But, according to Webster's New World, this one-word spelling of this adverb is correct.
Reminds me of a line from an old Simpsons episode (doesn't everything?). In a spoof TV infomercial for some cleanser, show hosts scrub the grime off the tombstone of Edgar Allen Poe. Co-host Troy McClure, dazzled by the results, exclaims: "Quoth the raven: What a shine!"