You need a TARDIS just to be able to understand the entire title of this book. Best I can tell it's officially Doctor Who: The Lost Adventure by Douglas Adams: Shada by Gareth Roberts. But Roberts' name isn't on the spine. There's a reason for that: Shada was originally a TV script written by Douglas Adams (of The Hitchhiker's Guide to the Galaxy fame) for the Fourth Doctor, even partially filmed but cut short by a strike. Roberts rewrites and expands the story as a novel, which is a particularly inspired choice because he's written at least two episodes for the new Doctor Who series that are both funny and thrilling in about the same ratio as Douglas Adams himself. He does a good job, in that it's a good story.
The end result is that it's about what you would expect. Some funny moments, a decent enough plot (a bit overstuffed and understuffed in parts), about the same as watching an average episode of Doctor Who, so I can't complain about that. It's not as sublimely funny as Hitchhiker's Guide or even as funny as "Closing Time" (my favorite episode by Roberts, you know, the one with the baby Alfie who in his own mind is named Stormageddon the Dark Lord), but it has its moments and works rather well for being patched together and spread out over time. That in itself is what makes it seem to fit into the patched together universe of Doctor Who. For those who can't wait for the next season to start in the fall, this is a fine substitute and good airplane reading too.