The Bagthorpe family are all apparently multi-talented, except for Jack (and his dog, Zero). So Jack and his Uncle Parker concoct a scheme to raise Jack's profile somewhat.
I didn't much care for it though - the Bagthorpes, as well as being multi-talented are egotistical, thoughtless and inconsiderate, so that it's hard to care about them very much. I did feel rather sorry for Jack to begin with, but his uncle's plan consists largely of deceiving the rest of Jack's family, for no particularly good reason, which didn't endear either of them to me.
I'm probably taking the whole thing way too seriously actually - I think it's really meant to be a knockabout farce, which I've never found all that funny. I suspect this was just the wrong book for me. Or I was the wrong reader for it.
At least it was rather more cheerful than Vampire$ :-)
Another one for the Bookmooch pile though.