Wasp Factory is excelllllllent
really, his SF and non-SF are equally good, it just depends on what you're in the mood for. Complicity was awesome but Wasp Factory is a very good starting point
I finished all his SF and was like, huh ... well I guess I'll read his non-SF? (I'd already read three of his non-SF books - just decided to turn his non-SF into a go-to "list") and really it's just as enjoyable
if you like it read Use of Weapons next !!
also, The Bridge is awesome, if you like Hard-Boiled Wonderland and the End of the World