There are some writers out there that are only as good as their ideas. When they come up with a good concept, all they need to do is get out of its way and let the story shine through. These writers tend not to be remembered as great wordsmiths, but that doesn't matter so much; their prose is nothing to write home about, but they've got such inventive, puzzle-box minds that you have to admire the purity of their plots even if none of the individual moments stand out.
In some ways, David Bishop (Who Killed Kennedy, Amorality Tale, The Domino Effect, Empire of Death) is the exact opposite of that kind of writer. He does come up with great ideas--in fact, I'd say that if you reduced every Doctor Who novel to a one-sentence synopsis, there'd be no question that these four would rank among the highest. "An outside-in view of the UNIT era, as told by an investigative reporter who believes them to be a sinister conspiracy!" "The Doctor teams up with the Krays to fight aliens in the East End in the 50s!" "Sinister aliens prevent the computer from being invented, and the Doctor has to free Alan Turing from the Tower of London to save humanity!" "Queen Victoria colonizes the afterlife!" All great stuff, but he doesn't seem to be able to develop them properly. It feels like he rushes through the follow-up work needed to turn a great idea into a great novel, and as a result books that should soar feel like they slog along.
'Empire of Death' is the perfect example. With the spiritualism craze going full-bore in the Victorian era, it seems like the perfect place to set a novel about the afterlife. (Arguably, it seems like a mistake to set it in 'Doctor Who', where you know you're going to have to undermine your own concept by hedging your bets on the exact nature of the Other Side, but let's grant him a bit of leeway on that because it's so easy to think that the Doctor can fit into any story concept and make it better.) Having a physical portal to the afterlife is also a great idea, because it allows you to contrast Victoria's obsession with spiritualism with her role as one of history's biggest imperialists. The scene where troops invade Heaven in order to conquer it for the British Empire is a fine piece of social satire.
But having come up with the idea, Bishop never seems to refine it. Long stretches of the novel linger on incidental characters and minor dramas, there's a strange anti-abortion sub-theme that's awkwardly shoehorned in and not allowed to develop logically (presumably due to concerns about controversy, but it seems odd to include the topic in the first place if you're going to remove any exploration of it) and the interesting parts of the plot don't really feature until the end, and then only tangentially. The characters are all stock Victorian archetypes who never inhabit their roles convincingly, the plot runs along on rails to a predefined conclusion, and at the end, the ghosts have to turn out to be aliens because it's a 'Doctor Who' novel. (As predicted at the beginning of the previous paragraph.) Ultimately none of it lives up to its potential.
A similar analysis could be performed for any of Bishop's novels (with the possible exception of 'Who Killed Kennedy', which succeeds primarily because it's a pastiche of a cheesy "true conspiracy" book and so the flaws in its prose and characterization feel like little marks of authenticity.) His characters always feel like they stepped whole out of TVTropes.com holding their Idiot Balls firmly with both hands, his actual plots run on forced coincidence and authorial fiat, and there's never any sense of surprise to any of his endings. (Admittedly, that's unfair in the case of 'The Domino Effect', which suffers from being part of an arc where none of the authors' books ever feel like they're part of the same storyline, but 'The Domino Effect' has other problems.) It's hard to escape the idea that Bishop is capable of writing a much better book than he has so far, simply because his ideas are so good; but that only exacerbates the frustration involved in reading them, because you're simultaneously rewriting them in your head to make the concepts involved work.
On the whole, I wouldn't say no to another novel by David Bishop, if for no other reason than 'Who Killed Kennedy' showed so much promise that I'd like to see him fulfill it someday. But I don't think his best work will ever be his 'Doctor Who' books, simply because I think he needs an editor who will challenge him to work harder on making his ideas click on the page, and I don't think that authors get that kind of personal attention from the editors in the 'Doctor Who' line. The deadlines are too stringent and the workload too great to force someone to go back for draft after draft after draft...and after reading all of David Bishop's output, I think the clearest impression I got was that his books had a draft too few.