Set in the same Universe and timeframe as David Weber's "Honor Harrington" novels, sometimes nicknamed the "Honorverse." The events take place at approximately the same time as the early chapters of "War of Honor."
If you have not read any of the other books in the series: this novel is set in the far future and is the story of how men and women from planets who are normally bitter enemies - indeed, technically at war with one another - collaborate against an unholy alliance of terrorist religious extremists, and corrupt corporations profiteering from a vile form of slavery and who are rich enough to buy governments.
If you are familiar with the rest of the series, be aware that this books has several differences from them.
With the most recent group of short stories and novels in the "Honorverse" Weber and his collaborators seem to be establishing three groups of characters and storylines, which they are all linked in a reasonably consistent manner into one history.
There is the main sequence featuring Honor Harrington herself, in which the first novel, and the best one to start with, is "On Basilisk Station." The most recent novels in the main sequence are "War of Honor" and "At All Costs." There is a "next generation" sequence featuring some younger officers in the Haven and Manticoran navies such as Helen Zilwicki and Abigail Hearns. And there is a series of spy stories, in which "Crown of Slaves" is the first full length novel. Honor Harrington does get a cameo part in the book, but the central figures are Anton Zilwicki, his adopted daughter Berry, Princess Ruth Winton, and the Havenite agent Victor Cachat.
The first main difference between "Crown of Slaves" and most of the other books in the Honorverse is that the main enemy is the genetic slavers, the companies who traffic in slaves (particularly Manpower) and the governments they have bought. Agents from Manticore and Grayson are practically allied with agents from Haven against the slavers, despite the fact that their countries are involved in a very bitter war. Hence Manticorans such as Anton Zilwicki can and do make common cause with Victor Cachat, the star agent of Haven's Federal Intelligence Service.
The second main difference is that the book is about espionage, politics, counter-terrorism and revolt rather than space battles. The only Manticoran naval officer who gets to fight a space battle is Captain Oversteegen, who despite being a cousin of the Manticoran Prime Minister, Baron High Ridge, has a mind of his own.
This is a well-written story, with a lot of excitement, a rather convoluted but clever plot, and interesting heroes and heroines, although the "bad guys" are sometimes so cartoonishly evil that they are a little hard to believe.
If you read the other "Honorverse" books purely for the space battles, leave this one alone. If you like the intrigue and the characters, you'll probably like this book.
If you have not read any of the Honorverse books, but like stories of
intrigue and revolt in the far future - think Aeon Flux but slightly more cerebral and plausible - you may well enjoy it.