Star Trek fiction, whether based on the series or based on original concepts, targets the same essential audience. With Doctor Who fiction there's more variation; the official novels being published today are targeted at a roughly 12 year-old audience, while the spin-offs are targeted differently at smaller, older, more literate audiences (with some variation, depending upon which line is in question). I'd call Articles of the Federation niche-y, I have the impression that your own Department of Temporal Investigations is niche-y, but the Time Hunter novellas were way super-niche-y.^We already have New Frontier, SCE, Titan, Vanguard, my upcoming DTI book, and the like. Okay, the Summerfield and Wildthyme books are different in that they're creator-owned and the publishers don't need a license for Doctor Who fiction (in fact, I gather that Wildthyme was an independent character first and only later added into the Whoniverse), but otherwise, is there a great difference in content or approach?
I'm curious to see what kind of reception Michael Moorcock's Doctor Who novel will receive this October, because it's an official novel but it's targeted at an audience that BBC Books hasn't tried to capture since 2005 -- and arguably even before then.