Iain M. Banks has established himself as one of the most highly regarded SF authors of the current generation. Unusually, he switches between genre and mainstream fiction (the latter under the name Iain Banks - without the M) and is equally successful at both. His SF books focus on a far distant future when mankind has spread across the galaxy. Most of them are set in the "Culture", a time of enormous wealth for all, managed by immensely powerful artificial intelligences.
The Algebraist is not a part of the Culture series, but it is still set in a galaxy-spanning future. Humanity and various alien races co-exist, using huge artificial wormholes to connect star systems. There has been a long history of inter-human conflict in which AIs have been banned. The action is set in one distant system which has been cut off from the rest of civilisation by the destruction of its wormhole in such a conflict, and can only be reconnected after a sub-light-speed fleet has spent centuries travelling from the nearest high-technology system. To add to their problems, the system is vulnerable to attack by dissident human cultures who are planning an invasion. A Jovian-type gas giant within the system is a home to the Dwellers, a galaxy-wide race which have been around for some ten billion years and who can individually live for up to two billion. They have no great interest in other races but permit occasional visits by human scholars.
One of these scholars is Fassin Taak, the hero of the novel. He is summarily recruited into the military/religious order which rules the system and sent to the gas giant to investigate an ancient rumour that the Dwellers know of other wormholes which could end their isolation. The action focuses mainly on Taak's adventures among the Dwellers, switching occasionally to other characters in the system, in the rescue fleet and in a dissident invasion fleet which are both racing towards the system.
Like all of Banks' books, The Algebraist is not really a page-turner. The pace is slow and deliberate and at over 500 pages of a rather small font, the book requires some dedication to read. I must confess that it took me quite a while to get into, but I stuck with it and eventually became so engrossed that I read the last third in one sitting.
The main point of interest in the story is the Dweller race, which lives in the atmosphere of gas giants. They are famously disorganised, appear to have no government, and normally use a relatively low level of technology. Banks makes them intriguing but perhaps too human-like in their attitudes and conversation; despite their vast age, strange habitat and decidedly non-human physical form I didn't find them as alien as I would have expected.
I found this book to be well worth reading, but while I admire Banks' works (with the exception of Feersum Endjinn, which I abandoned in irritation at the extensive use of an invented dialect) they never quite hit the bullseye with me. I'll still keep reading them, though.