Jacob's book is about a boy discovering its magical powers and was published in 1987, ten year before the JK Rowling's first Harry Potter book.
Jacob's book was also rejected by Rowling's present publisher, Bloomsbury Publishing. He got his book published by smaller company under the title The Adventures Of Willy The Wizard No 1: Livid Land. Jacob died in 1997 after loosing all his money in the stock market crash of 1991 before Harry Potter hit the markets.
In both 'Willy the Wizard' and 'Harry Potter and Goblet of Fire' the boys competes in a magic contest, and boys try to rescue human hostages held by half-human creatures from a bathroom. The lawsuit that is based on such similarities will has been filed in High Court against Bloomsbury.