The Wall Street Journal had a review today of David Crystal's "Spell it Out." It sounds very interesting; here is an excerpt from the article:
No account of English spelling can overlook the influence of William Caxton, who introduced printing to England in 1476. The author shows that Caxton's pragmatic approach had some unintended effects. Caxton brought in experienced compositors from Bruges. They spoke Flemish, and their knowledge of English was less than perfect. They spelled English words in ways that felt right to them, resulting in an English that had a distinctly Flemish hue. This is why we find an h in ghost: In Flemish the word was gheest. The h spread to related words, such as aghast and ghastly. But in other cases the Flemish tinge didn't last: In Caxton's texts there is an h in goat and goose.