True — Xenophon of Ephesus, Chariton, Achilles Tatius can be tiresome... good bedtime reading. But Longus and (for very different reasons) Heliodorus are in another league!

For koine, the Greek Novelists are also lovely. The quality varies but Longus in particular is stunning — a masterpiece of pseudo-naive plain style (with intermittent flights of Gorgianic patterning — perhaps like English Euphuists, but better?). Goethe apparently read Longus every year.