The Lowlands are home to many kinden, humans who share characteristics with different types of insects. There are beetle-kinden who are short and stout and are inventors, mantis-kinden who are excellent duellists and fighters, ant-kinden who are great soldiers due to there hive-mind, spider-kinden who are able to climb any surface and so on. And then we have the wasp-kinden who are the empire mentioned in the title. Their special ability is that they can create a 'sting' to attack their enemies as well as all wasp-kinden being warriors who use slaves to make their society function.
As the wasp empire begins to encroach on the Lowlands one beetle-kinden, Stenwold, has for years been warning about this coming threat but no one has paid him any mind. Therefore he must send off a small group of operatives to try and protect the world from the growing darkness.
This inventive premise is wonderfully used by Tchaikovsky to tell a great story that will leave you hanging out for the next book, Dragonfly Falling.