"Just plain fun" is tricky. One one person finds funny, another might just find silly.
But IMO you could do a lot worse than any of the Jeeves and Wooster stories by P G Wodehouse. Since you're in the US, perhaps you could start with one of the early novels,
Right Ho, Jeeves, which is in the public domain in the US, as the copyright wasn't renewed.
http://www.gutenberg.org/ebooks/10554