Wizard's Holiday is the latest one and is just as good as the others. It's a perfect blend of fantasy and science fiction--when one thinks of wizards one automatically thinks of Gandalf or Harry Potter and fantasy. But in Duane's universe, wizards are more scientific--they can manipulate the world but only within the laws of science.
In this particular installment, Nita and Kit are on "holiday" on a distant planet. Nita's younger sister Dairine signed Nita and herself up for an excursus--a wizard vacation--but was not authorized to do so. As punishment, she was not able to go, but the excursus was approved. So Nita took Kit along instead. In exchange for Nita and Kit (and Ponch the dog), three aliens were sent to Earth for an excursus and stayed with Dairine and her dad. Since wizards never really get a vacation, both sets of visitors wind up getting involved in a lot more than they anticipated...
I love all of these books. I hope Duane continues writing them.
On My Nightstand: So many, I can't even list them all