Vacuum Diagrams is a collection of short stories set in Baxter’s Xeelee universe (as explored in the novels Raft, Timelike Infinity, Flux and Ring), but far from being a collection of odds and ends this probably stands as the ultimate Xeelee book. The stories are laid out in chronological order, and together with linking material this forms a complete history of Baxter’s universe, from Big Bang to the ultimate destruction of all baryonic life.
The stories themselves are mostly enjoyable, although Baxter’s problems with shoehorning in hard sf exposition with storytelling are often evident. Its also noticeable how Baxter’s earlier tales are much more light-hearted than his later, more confident work. A number of the stories also seem to be either direct or subtle lifts from his novels, (eg; Stowaway is a direct extract from Raft, while Hero takes an incident from Flux and retells it with a different spin), though its difficult to tell if these were short stories that were later developed into novels, or cynical reworking to sell the same idea twice. The quality remains high though, so even when a tale such as The Baryonic Lords is obviously just a dry-run of the novel Ring, its still enjoyable stuff. Possibly the biggest criticism of the collection is the lack of range of the stories, most concentrating in a rather narrow band of classic hard sf ‘new invention/discovery’ format.
All in all though, if you are only going to read one of Baxter’s Xeelee novels, this should be the one.