Ted Chiang is the thinking person’s sci-fi inventor, a writer of amazing short stories in the tradition, perhaps, of Phillip K. Dick. Chiang’s output is not prolific but a piercing intelligence illuminates his eclectic body of works. He might well drift in obscurity, except his most famous story was made into the stunning sci-fi movie “Arrival.” Now his second volume “Exhalation.” showcase seven short stories published over the last decade and a half, plus two new tales. All of the stories vary in subject matter, style, tone, and plotting. All of them make the reader think. A handful seem didactic but if these aren’t what you come to sci-fi for, rest assured. There are at least two long gems here. “Anxiety Is the Dizziness of Freedom” posits a world in which commercially sold prisms let you interrogate your alternative realities a little apart from you own. And “The Lifecycle of Software Objects” is glorious, a galloping tale of avatar-style software-bound “lives” tended by a zookeeper. Ted Chiang celebrates imagination at its most free and lyrical.