I loved this book, the only issue is that it uses methods that are too familiar to the reader to introduce the characters that the opening really wasn't as exciting as it should have been.
The book opens with a legion, the death guard fighting some Xeno race. This is how every legion and character has been introduced so far, with the legion wiping out some xeno world, or non compliant world. It just didn't feel like an original way to open the book and introduce the characters, but its only a small complaint.
The characters introduced are excellent, Garro shines above all others. The book takes place around the time of the 3rd book, and even has a scene from garros perspective fighting in a temple alongside Saul Tarvitz. The same battle was in Galaxy in flames from Saul Tarvitz point of view, so the scene is a little odd as we know exactly what is going to happen, you just see it through another pare of eyes.
Garro is a brilliant character, he has even spawned his own series of audio novels, and the book follows his perspective, fighting xenos, then Issvan 3, and his escape with a few characters from the opening trilogy. Although many of the events, battles etc have been talked about or in some cases even scene through different eyes, it is still an incredible book with exciting battles, and a great twist. Unmissable.