Spoiler alert! This review reveals significant plot details.
Karl Schroeder demonstrates an impressive capacity for worldbuilding and imaginative hard science fiction. Sun of Suns is truly awesome in the scope of its technological milieu. The civilization of Virga, with artificially-generated gravity, is as alien to us as the idea of "Artificial Nature" is to the isolated Virgans. Set against this majestic backdrop, the protagonist, Hayden Griffin, is on a mission of revenge that quickly becomes complicated.
Quixotically, Schroeder spends very little time actually allowing us to get to know Hayden. As a result, I found it difficult to relate to the main character--not because I lacked empathy, more because I just didn't know much about him. The story begins when Hayden is a young adult, then jumps forward six years after the massacre in which his parents die. Apparently, Hayden spent the interim with pirates, but Schroeder reveals remarkably few details. On one hand, I admire his ability to avoid what some may consider unnecessary exposition--Hayden only brings it up when it's relevant to the plot. On the other hand, this backstory is important in establishing who Hayden is; I felt its absence throughout the entire novel.
Some of the other characters are far better fleshed out than Hayden. Venera Fanning was a fun and ruthless antagonist with an interesting—and explained—background. Likewise, her husband, Admiral Chaisson Fanning, is a dedicated and patriotic man who is willing to sacrifice his life to protect his nation. In time, they come to rely upon Hayden--and to some extent, he relies upon them--even though Admiral Fanning is Hayden's target for vengeance. I appreciate Schroeder's attempt to introduce moral ambiguity; the tenuous environment of Virga lends itself to the idea that people who are enemies may suddenly become dependent upon one another.
The posthuman universe outside the fullerene barrier of Virga's balloon shell was intriguing. I can only surmise that such an important plot point will be developed further in the next books of this series. Likewise, I found Hayden's love interest, Aubri Mahallan, intriguing but lacking much depth. She seemed marked for "tragic love interest" from the moment she appeared, and Schroeder played the trope straight enough that I had to look away. Her motivations seemed more driven by plot than by character, and her death was almost as needless--although perhaps not as melodramatic--as that of the Rook's chartmaster.
Oh yes, death. There's quite a bit of that in Sun of Suns, beginning with the deaths of Hayden's parents. Lots of fighting and adventure too--this would make a good movie if anyone figured out how to actually film it. For those who thirst for swashbuckling adventure, this book has it all: pirates, vehicle chases (bike chases through air, no less), sword fighting, and free fall aerial manoeuvres. Yes, this book is action-packed. And I am not being sarcastic when I say that this is a redeeming feature. Although I'm not one to enjoy an excess of action, Schroeder makes it a cornerstone of his story. It makes up for the lack of description of characters or environment (beyond the scientific explanations woven into the dialogue). The action elevates Sun of Suns from amusing posthuman rumination to entertaining work of hard science fiction.
Schroeder has created a fascinating world around which to weave a series. I hope (probably in vain) that the next book has better, more three-dimensional characters. Alas, that sort of improvement doesn't seem likely, and the mediocrity of Sun of Suns's protagonist consigns the book itself to the unpalatable category of "good, but not great."