The influence on steampunk literature goes as far back as H.G. Wells and Jules Verne, but those authors can't really be considered steampunk because they were writing about their own era. Michael Moorcock's "The Warlord of the Air" (1971), "Lord Kelvin's Machine" (1992) by James P. Blaylock, "The Difference Engine" (1991) by William Gibson and Bruce Sterling, and Di Filippo's "Steampunk Trilogy" (1995) are often cited as the central steampunk novels. In "The Difference Engine," the visionary artist William Blake gives Powerpoint presentations using a kind of magnetic tile device. In a novel released this year, Jay Lake's "Mainspring," the sun revolves around the earth along a system of celestial gears.
If anyone in the Boston area could send me the hardcopy, I'd be much obliged.