Now with Tepper I'd have recommended Beauty, which I absolutely loved, and it's generally had good reactions from a lot of other people too. I've not really delved into the earlier ones (which I am assured are the most horrorish) - the later ones are pretty good, but suffer a bit from being essentially the same story over and over again in different settings, and get quite wearing on after your sixth book or so. Partly because as you go along, the worldview she presents gets familiar, with the bits that grate grating more and the good bits fading into familiarity.

Still, Beauty is a bit different, as is The Fresco (featuring one of the most amusingly if-only-it-could-be-done-for-real actions ever taken by a bunch of Earth-visiting aliens). Apart from Beauty I'd say the best of her's is probably Grass, being a particularly well done example of the Tepper-story.

I'm always willing to lend Tepper books to people - in particular, I'm dead keen to evangelise Beauty to people.