So I checked the date on the novel, and it was published in 1993. That means the author used a slang word before its spelling had solidified into something else. This isn't the first time I've encountered that problem.
In reading some of the L. Frank Baum "Oz" novels (circa 1900), I came across the spelling wierd. Now, this word has always bothered me, because the 'i before e' rule' says it should be spelled as Baum spells it. How did we settle on weird as the spelling instead? It was spelled as "wyrd" in Beowulf, but the online wordorigins.org dictionary says that the current spelling was codifed by Shakespeare, based on the Scottish use of the word to mean "witch." So, Baum's spelling is probably a typo instead of an alternate spelling.
A friend who wrote movie reviews in the early 90s frequently used ditsy as an adjective, without realizing that the rest of the world spells this as ditzy. I'm still hung up on dingy (which means much the same thing to Americans as "ditzy") being a homograph for the "dingy" that means something is not entirely clean. I hate homographs. I have the urge to spell the second usage as "dingey" instead, but I've been outvoted. Someone on Urban Dictionary has confused both with "dinghy" (the boat), though, so I'm still ahead of the game. ;)
Now, "usage" is a word whose spelling I don't like. It's similar to "usability," which is a word now common in my profession. I would prefer both of those to be spelled with an extra 'e', as in "useage" and "useability." Otherwise, they look like "us-xxx" to me, and I can't help reading them as if they imply other things related to the word "us":
"This apartment is full of usage-- our photos, knick-knacks, and combined furniture. There are so many memories here."
"But does this relationship have enough usability for the long haul?"
Although the 'e' is normally dropped when a suffix beginning with a vowel is added, this isn't always the case. My paperback "Merriam-Webster Dictionary" notes that either likable or likeable is an accepted spelling. I have less trouble with "likable," though, because "lik" itself is not a word the way that "us" is. Lik may bring out the giggles in the twelve-year-old part of one's mind, but that's because it resembles another existing word (which has the associated slang of "lickable," as in, "Brad Pitt's chest is very lickable.")
What words do you think should have been spelled differently?