Robert J. Harris 
Thor Is Locked In My Garage! [EPUB ebook] 

Brothers Greg and Lewis are enjoying a heatwave in the summer holidays — until Loki, the god of mischief, buries St Andrews in a huge blizzard! Loki is determined to conquer the universe and will stop at NOTHING to get his way.
Greg, Lewis and their friend Susie must make a perilous journey to Asgard, the City of the Gods, to foil Loki’s evil plan.
Luckily, Thor, the god of thunder, has turned up to help them. Unfortunately, he’s locked in the boys’ garage…
The hilarious sequel to The Day the World Went Loki is filled with monsters, mischief and everyone’s favourite Norse gods.