The books I rate most highly in my life are the ones which inspire me to write. It's sort of like the Olympics voting - there are marks for characterization, language, plot, and inspiration. Does the author's voice make me want to write?
Among those authors that rank high in that last category are Louisa May Alcott, Margaret Atwood, Geraldine Brooks. If I'm in the right mood to be inspired, one of these three (well, Atwood especially) will do it for me. Reading their novels is like drinking the kind of $100/bottle merlot you splurge for on your anniversary. Their stories, their language, are intoxicating, and make me believe I can write anything - but particularly that I can write something fantastic.
If I'm not in a mood to be inspired, there's just one author that gets me going - Tamora Pierce. Oddly, I've only discovered Pierce in the past couple of years. Reading any of her Tortall books is more like drinking a solid, tried-and-true table chianti. There's a nice taste, it complements just about any mood, and I get just enough of a warm glow to pull me out of the writer's block I didn't know I was in.
A few other authors I turn to for inspiration, rather than enjoyment only, are Jasper Fforde, Diana Wynne Jones, Charlotte Bronte, Robin McKinley (and, of course, many of my blogosphere buddies.) How about you? What authors inspire you?