Defiance — Susan Kaye Quinn

Most of humanity has ascended into hyper-intelligent human/machine hybrids, but legacy humans like Cyrus Kowalski are used to skirting the laws they've laid down -- after all, he knows the ascenders only pretend to care about the legacy pets they keep. But when a woman Cyrus loves like a mother is stricken by a disease the ascenders refuse to cure, he has to decide how far he can go without getting banished from the legacy city that's always been his home. 

Defiance is a standalone novella that provides a glimpse into a dark corner of the Singularity novel series.

The Stories of Singularity can be read independently from the Singularity novel series.