In fact, I'm almost finished with it now. My usual review to come.
In answer to your query, the story comes after all Thrawn-based novels (though not published in that order). It will spoil several things if you read it first.
*edit*
That said; I don't know if it will spoil Outbound Flight, the novel it addresses. Since Outbound Flight is Prequel-based, I didn't bother with it.