Mage-Captain Ivan Halloway managed to retire from the Royal Martian Navy without seeing combat. He's a coward, so better to be retired rather than serving in the coming civil war. Back home in the Xanth system he's uncertain what he wants to do with the rest of his life, so he agrees to help an old friend. He should have gotten more details before he agreed! Karl is deeply in debt following a divorce and mid-life crisis that saw his entire crew resign so he's going to enter the illegal Black Pulsar Race, an obstacle course around a binary pulsar system run by crime syndicates. One reason it's illegal is that twenty-five percent of ships don't survive to the end, but Karl is confident the Restoya can win. The prize money will allow him to pay off his debts and keep his ship. Ivan's not a fan of this plan, but he does want to help Karl until the mob threatens to kills both of them unless Ivan helps them take the Restoya during the race. He agrees on the condition they don't harm Karl and forgive his debts, but he still has a bad feeling about this.

As a novella in the Starship's Mage universe it helps to be familiar with the world building because Stewart keeps the explanations very brief. From Ivan's point of view things start out desperate and quickly devolve from there. Karl gives Ivan a tour of the modifications he's made to the Restoya which cover why he's sure he can win the race and also just why the mob wants the ship so badly. Home engineered tech apparently triumphs over physics and biology; just go with it. The race itself is mostly distilled to one action sequence where we see why so many ships fail to survive the course and when it comes down to it Ivan proves that you don't mess with a Mage-Captain of the RMN, even if he's retired. 

Pulsar Race is available in E-book and is included in Kindle Unlimited like most of the Starship's Mage series. It is available on Audible with the series narrator Jeffrey Kafer. Please note, the Audible edition also includes a second novella called Excalibur Lost