Peter Watts’s "Echopraxia" is a tour de force in the hard sci-fi genre. Peerlessly cerebral and phenomenally gripping, it proves to be not just a book, but a vortex that pulls you in, page by page.

The main theme echoing throughout the novel is the illusion of free will — a question that has puzzled humankind for millennia. This theme, cleverly woven into a multilayered narrative extolling a hypothetical world both fascinating and terrifying, sets a compelling backdrop for the story.

Readers seeking light-hearted, breezy reads might find themselves challenged. "Echopraxia" is not for those looking for a casual dalliance with science fiction. It is an immersion in hard sci-fi, dense with scientific concepts, philosophical ideas, and it pulls no punches when it comes to its narrative complexity. Those seeking a book as mentally stimulating as it is adventurous will appreciate what "Echopraxia" brings to the table.

Adding to the fundamental brilliance of the book, Watts provides author's notes that are equally captivating. If you can procure an edition that includes these, you’re in for a treat. They serve to enhance the depth of the narrative, making the complexities and proficiencies of Watts's mind even more accessible to us as readers.

In conclusion, "Echopraxia" is a triumphant exploration of post-humanism, neurology, artificial intelligence, and so much more. It provokes thought, raises important questions, and still manages to be a fun, engaging read. Truly, an accomplished feat in the realm of hard sci-fi.