Lyn Funnell 
Willy the Whizz and the Wormhole [PDF ebook] 

Will Spalding had an IQ of 172. But nobody knew it yet. And nobody would realise it even when he constructed what was probably the most amazing invention that the world had ever seen. Actually most of the world would never see it!Read the hilarious story of what happens when Will’s little sister Maud crawls into it, and how Will and his friends (with the help of Einstein the dog) try to get her back without Will’s Mum Pru finding out.