Mr. Prohack by Arnold Bennett (1867 - 1931)

Mr Prohack, an ordinary official in the Treasury and leading a hum-drum life, suddenly and unexpectedly inherits a large sum of money which, with a lucky investment, he turns into a fortune. This humorous book follows his progress and that of his wife, son and daughter who all, in their different ways, slowly get used to their new lives. - Summary by Simon Evers