My biggest deal-breaker is a simple one: deus ex machina. This translates to “god from the machine,” meaning that something not previously covered suddenly appears to bail out our hero/heroine.

Take “Harry Potter and the Deathly Hallows.” With what spell did Harry defeat Voldemort? “Expelliarmus.” Now when the hell did he learn that???

Simple: back in “Chamber of Secrets.” Potter used that spell repeatedly throughout the series, so it was a known quantity. This was NOT deus ex machina. It was good writing (and truly brilliant foreshadowing).

Deus ex machina would have been if Harry had dropped his wand, but suddenly remembered he had a Colt Desert Eagle .45 in his pocket, then pulled it out and shot Voldemort in the head. When were guns ever mentioned in the Harry Potter mythology (except for being mocked as “a sort of Muggle wand” in “The Daily Prophet.”)? Nobody at Hogwarts would have ever seen a gun, much less suddenly had one in his pocket.

When the trio fled the wedding party, and Hermione had the small handbag that was bewitched to hold a metric ton of stuff, that bag’s existence and properties were implied earlier when she was  planning which huge stack of books to take. Also, Hermione is definitely the brains of the outfit, and I have no doubt she could bewitch the bag to hold all that stuff. The spell itself was referred to in an earlier book, when Hagrid gave Harry that mole skin pouch that held more than it should have. Again, not deus ex machina.

If Ron Weasley had cut Voldemort in half with a chainsaw he found on the Great Hall floor? Yeah.

Every so often, I read a book where the author loses control of his or her story, and can’t regain it without resorting to this cheat. What this does–having a troupe of flying monkeys fly into “JFK” and whisk away the President before the shooting starts, e.g.–is cheapen the novel. If the author reduces him or herself to that sort of chicanery, the rest of the novel loses all credibility, and my respect for the author disapparates to the cornfield. The author becomes dead to me, and I will likely never read his or her work again.

Oh, I admit it’s kind of fun when Sherlock Holmes pulls something seemingly impossible out of his ass, then explains to Dr. Watson later how he happened to have a javelin in his breeches, but if you’re Sherlock Holmes, you can get away with that. We almost expect that he’ll pull something out of thin air, but we know he’ll justify it in the denouement.

Most deus ex machina is just bad writing, plain and simple, and I will smite the author (or at least never pick up his or her work again).

Complete factual impossibilities off-piss me a great deal as well. I read a horrible book a few months ago. One of the characters was a vampire, and his human friend was flying with him over the Atlantic to get help. Or something. I’ve suppressed it. Anyway, the vampire starts having withdrawals, so the two men go into the airliner’s bathroom, and the human PULLS OUT HIS PENKNIFE and cuts himself so that the vampire can feed a little.

HE PULLED OUT A KNIFE! The book was written in 2010, waaaaaay after 9/11. You can’t carry most nail-clippers on an airliner these days, much less a knife. My dad has a tiny Swiss army knife on his keyring. Going through security in the Phoenix airport two weeks ago, they confiscated it. Seriously.

I guess the point would be this: as an author, you create a world. We, as readers, buy into your world. Make sure your action is valid within the world you’ve created. If you’ve written a gritty noir detective story set in San Francisco–say you’ve called it The Maltese Falcon–for the love of everything holy and literate, don’t have Sam Spade disarm Joel Cairo by using a wand and “expelliarmus.” Have Sam Spade bitch-slap Joel Cairo and take the gun. That works.

Then again, I would have forgiven the deus ex machina violation if Sam Spade had appeared in Hogsmeade and bitch-slapped the bo-shit out of Harry Potter’s whiny, petulant ass in “Order of the Phoenix.” (Furthermore, I’d have campaigned for Spade to receive the Order of Merlin, First Class, for that necessary beatdown ex machina)

Happy Monday.  Besos, t