Spoiler Level: Medium
Not Gary Russell's best, but still an entertaining read... especially the last third.
Business Unusual is a direct follow-up to Scales of Injustice (which I read and reviewed last October). In this book we learn what's happened to the creepy guys who were running the psuedo-Torchwood Institute since the previous book.
We also get to meet Mel properly. Since Colin Baker was dissed and dismissed as the Doctor after "Trial of a Time Lord," where Mel had been "introduced" by being plucked from his future, we were never given an explanation in the show proper on just how the Doctor could leave with a companion from his own future. And then he goes and regenerates in the very next story!
Well, the only solution is to assume that a lot has to have happened between "Trial of a Time Lord" and "Time and the Rani." And the show does at least give a great opening for it-- at one point in "Trial," the Doctor gives his age as "900 years, more or less." Then in the next story "Time and the Rani," the newly-regenerated Seventh Doctor gives his age as 953. So we have to assume that 53 years ("more or less") have taken place between the two stories, giving the Sixth Doctor room to do a whole lot more.
And the books (and audios) have run with that, much to my delight. The mythos goes that the Doctor dropped off Mel back in her proper place in time, became a hermit for a little while, traveled around with Grant and then Evelyn (and Frobisher in there somewhere) and then finally ran into Mel the way history intended him to. Then his TARDIS gets whacked by the Rani and he regenerates.
None of which is really explained in this book. Business Unusual assumes that you at least know that the Doctor dropped off "Future Mel." I can see how a more casual fan may have been scratching is head and going "But how did the Doctor end up not being with Mel in the first place?" But then again, if you're a casual fan, you're probably not reading this book.
What this book does do is show how the Doctor has been going out of his way to avoid meeting Mel. Because if he changes his timeline enough that he never meets her, then perhaps the Valeyard will never be created as well. And that's really the fun part of this book-- seeing the Doctor trying to avoid his own destiny with Mel from happening.
There's two ways that this book fell a little flat to me. The first is the villains. The Irish Twins and the Managing Director from Scales of Injustice make for good heavies, but not very interesting as lead villains. And did I mention this book has the Brigadier in it? He's fairly prominent, which should be a good thing-- after all, Colin Baker is the only classic Doctor he didn't get a full story with. Only in this one, he still doesn't-- they don't meet up until the last 30 pages. Which is a real disappointment.
There's still some good old Russell "fanwank"...the Managing Director has still been scavenging leftover alien tech, so we get some nice references to the Doctor's adventures on Earth.
As I mentioned above, the last third of the book is when it all gets really good-- all the characters are in place and we start figuring out what the agendas really are and who's really using whom. And the Doctor's getting down to crunch time with Mel.
So all in all, it's still a worthwhile read.