Alternate universes always have a strike against them from the very start, especially if it's a universe that's destined to either revert back to the normal universe our heroes inhabit or destined to be destroyed. Why should we care about these incidental characters that the author is inventing when what happens to them won't really matter that much? It's even more of a problem in a continuing series, because the "universe" the main characters inhabit is consistent from book to book, making the alternate universe even more disposable than it normally is. The Infinity Race is an alternate universe novel. The events of Time Zero have caused the universes to diverge, so this is not a spoiler. Messingham has succeeded in making a book with characters that we somewhat care about, though the fact that the main characters keep hammering home the alternate aspect of their location makes it hard at times. Thus, Messingham manages to squeeze a pretty good book out of the whole concept.
The planet Selonart. A world that's almost all ocean, crystal clear waters shining in the sunlight. It's also home of the Trans-Global Regatta, which is "the ultimate sporting event in the universe!" Multi-stellar corporations from all over the Earth Empire enter sailing ships into this race for interstellar prestige...and lots of money, of course. But the mysterious Sabbath has his own agenda for the race. One that may wreak havoc on the timelines. The water on Selonart has unusual properties of propulsion, but they also have other mysterious properties. The Selonart colonists seem to be greatly affected by them, so the corporations put them to use on their sailing ships. But Sabbath has other plans for them. The Doctor and his companions land on Selonart and must not only stop these plans, but figure out what they are, before it's too late. For the Doctor, and the rest of the universe.
The Infinity Race is told in an unusual format. There is the normal third-person narrative, but there are also alternate journal entries from Anji and Fitz telling their part of the story, with the occasional piece by Bloom, the main Selonart native character. The Bloom entries are interesting because we see the change that comes over him as events happen. His entries start out with very broken English, making them a little difficult to read. They slowly get better as time goes on and things come to a head. He's also the most interesting character in the entire book, and it's neat to see the transition he goes through. The other Selonart natives, however, aren't anywhere near as interesting and do more to illustrate Bloom's character than anything else.
Anji and Fitz get a lot of characterization through their entries, and it's probably the best these two characters have been written in quite a while. The entries reflect their personalities perfectly, with Fitz displaying bravado but admitting to himself when he's really scared of what's happening. Anji starts out lamenting being pulled from her normal life that she had tried to get back to in Time Zero, is never afraid to point out when the Doctor's being a git, and finally comes around as she decides that what they're doing is necessary. What's most interesting about her sections is when the Doctor asks her to stay behind and talk to the governor and find Fitz. When she can't do either one, her frustration screams off the page, and her fear when the riots start is almost palpable. Sometimes the breezy way they write is a little irritating, especially when they get self-referential. They talk about endless corridors and how the seemingly never-ending "capture, escape, capture again" sequence happens again. But overall, these sections were quite good.
The Doctor is his normal dynamic self, which is nice to see. His interactions with Sabbath are wonderful, with both men being well-characterized. Their dialogue crackles as they argue the merits of their respective positions. The Doctor is adamant that Sabbath's plan not only can't work, but will destroy everything. The only unfortunate thing in The Infinity Race is that Sabbath takes on a couple of bad Master habits (the Master is an old enemy of the Doctor's). He rants and he raves, and he has an ambiguous fate that looks really bad but isn't deadly enough that he won't come back sometime.
Other incidental characters are more hit and miss. The governor is way over the top, and while that may have been intentional, it didn't make him any less annoying. Some of the other characters are better, but they are perfunctorily killed off, without any real purpose, after they've been around for a while. Messingham also suffers from the "let's introduce a character and give him some character detail just so we can kill him off" syndrome. It's a cheat to wring a little bit more emotion out of the reader, and it annoys the heck out of me.
The more I liked some of the characters, though, the more that the constant references to alternate universes annoyed me. I was beginning to like a couple of them, and I didn't want them not to "matter." My mind wanted to prevent me from investing too much caring into them because they would ultimately disappear, even if they didn't actually "die." That's the sad part of the book. Ultimately, it was an enjoyable read, and I'm glad I did. Give it a shot.