The series is good and an excellent choice for any one who likes Fantasy with a little Science Fiction. It is worth reading all three books this one was the worst of the three. I felt it just left too much hanging. I do not mind series books but I think each book should alos stand on it's own and this series does not do that.
Child of the River is an interesting example of big dumb object SF, and I find it entertaining. While the Confluence is interesting, it isn't the star (the Confluence is a rectangular platform in orbit around a blackhole and star - it tilts itself to give day and night cycles as well as using engines maintain its orbit). The nightsky of the Confluence shows evidence of massive tampering with the Galaxy - it now only has three arms, as well a more ordered groups of stars. Yamamanama (shortened to Yama) and the near human inhabitants of the Confluence are the stars of the book.
Yama is an orphan found near the end of the river and raised by a local official in the city of Aeolis, known for its crypts and tombs. Yama is a unique individual - his bloodline (human variant) is unknown and finding out who his people are drives him (along with his dreams of becoming a soldier). Apparently, Dr. Dismas (the local member of the Guild of Apothecaries and Chirurgeons) has found something of Yama's bloodline in the great city of Ys, but is being cagey with it.
From there, Yama is off on an adventure.
Child of the River tells the story of Yama, a young man of unique heritage in a world of genetically altered beings. The river world Confluence is a place of crumbling, ancient cities and machines so old and mysterious they seem like magic. From the vast necropolis of Aeolis to the engimatic metropolis of Ys, Yama seeks the truth about himself, and the universe. With Child of the River, McAuley begins a trilogy examining the death of a breathtakingly epic civilization.