Summary:
James Speckman is a pilot for a large delivery company, and along with one GELF that was hired by the company (not under contract anymore) (PL9-2130), goes from the company warehouse hub to outlying planets. His latest delivery is to an extremely remote colony on a moon, and things go wrong soon - one of the engines on the ship fails as he attempts to land, and he crashes.
The atmosphere is contaminated with fungal spores that very easily grow in people’s lungs, which means as soon as he steps out of his ship he’s doomed. Doomed to get genetic modification. People on the moon need increased lung capacity to combat the fungus in their lungs, so they need an extra pair (of lungs). Getting an extra pair of lungs requires significant body rework, including another chest cavity.
Everyone on the moon is a taur. James must become one as well.

Set in the GELF universe - that is, the same sci-fi universe as Not Dangerous At All. GELF is short for Genetically Engineered Life Form. They're anthromorphs that have a contract of indentured servitude for up to a hundred years.