A writer named Charlie Stross just posted a fascinating article on his blog about why novels are the length they are.
The reasons have to do with market dynamics — costs faced by publishers and bookstores. In the Victorian era, novels could get tremendously long because they were published serially: writers could go on week after week providing chapter-length installments indefinitely, until either they or their readers threatened to get bored.
And remember those fat mass-market paperbacks in grocery stores in the 80s and 90s? Publishers had been forced to raise the prices on paperbacks owing to inflation, and distributors “pushed back,” according to Stross, demanding fatter novels for the higher price. (Production costs weren’t much higher.) Hence all those 4×6″ doorstops by Stephen King. Stross concludes with the hope that ebooks, if widely adopted commercially, will separate considerations of form from production considerations for the first time in history. Which is a thought we’ve heard before, but it’s an interesting piece all the same.