Having finally figured out how to approach a book featuring Minds as the primary protagonists in Excession, here Iain M. Banks approaches another of the difficult elements of his Culture universe: the Sublime, that step off into another reality, or retreat into the tightly wound other dimensions that are one of the models of the universe we have now. Following a society at a similar tech-level to the Culture (a potential Culture founder, in fact, which decided not to join) as they approach their entry into the Sublime. The sublime itself remains an unexaplained, in fact pretty much unexplainable mystery, but the way a civilisation approaches it and the general attitudes of the Culture towards Life, the Universe and everything non-sublimed is explored using this mechanism. The Hydrogen Sonata of the title is a piece of music written for an unimagined instrument, which had to be invented in order for the piece to be played. The reasons for and structure of the piece and instrument are described in the book, as is the principle character, a member of the race approaching sublimation, who has set herself the highly difficult task of playing the piece “perfectly” before the sublimation. She is torn away from pursuit of this by the major events chronicled in the book, featuring the deep secrets behind the holy book of the subliming race. The Sonata is an interesting reflective sphere within the book, much as the play is within the Book of the New Sun, providing a microcosm of the overall situation and its eventual denouement. Along the way we are treated to Banks’ peculiar imagination, though not much of his trademark gut-churning.

A good addition to the Culture stable, though not receommended for first-timers to that universe.