A new word, the opposite of a catastrophe. From the paper:

… one of the hottest trends in the [mystery] genre is the so-called clerical mystery, in which the detective is not a cop but a minister. … Christian apologist J.I. Packer once observed that mysteries "… are Christian fairy tales, with savior heroes and plots that end in what Tolkien called a eucatastrophe – whereby things come right after seeming to go irrevocably wrong."

It's an interesting word, though it takes on a little different meaning from the opposite of "catastrophe," doesn't it? In Langmaker's Dictionary on Neologisms it says that it means "happy ending." Isn't that somewhat different from the antonym of disaster or a mishap or a fiasco? It just seems that "happy ending" is too general.

Well, J R R Tolkien coined eucatastrophe (from the Greek adjective eukatastrophos 'brought ot a good conclusion, well-turned (of a period)'), so I suppose his definition is a good one. It's not just any happy ending, but a sudden one. (He also worked as an assistant editor on the OED in the early part of the 20th century.) Greek καταστροψη katastrophē has several meanings: 'overturning', 'subjugation, reduction', 'return (of a vibrating string to axial position)', end, close, conclusion; denouement', 'ruin, undoing', and 'crane'. It consists of the prefix κατα- kata- 'down(wards); thoroughly' and the word στροψη strophē 'turning; twist; winding up (of a winch); transmutation (of metals)'. Some related words in Greek: akatastrophos 'never-ending', our old friend apostrophē 'turning back; twisting;turning away; resort, recourse; apostrophe; aversion;diversion, amusement; elision', isostrophē 'correspondence', metastrophē 'turning from (one thing) to another; turn (of events)', peristrophē 'turning or spinning aroundm courses of stars; whorls (in hairgrowth)', and many more.