The Mystery of the Merry Magician — Ellery Queen Jr.

When Ellery Queen goes out of town, his nephew takes on a cosmic case

For weeks, Gulliver Queen has looked forward to going on vacation with his uncle Ellery, the world-famous author and sleuth. But on the eve of their departure, Ellery is called away on government business. Gully is heartbroken -- until Ellery deputizes him as his assistant, tasking him with taking down information from anyone who comes by looking to hire the great detective. There is only one rule: No solving mysteries! But Ellery hasn't been gone an hour when Gully gets a case he cannot resist.
 
The client is Fisty Jones, a rough-and-tumble citizen of the New York docks who claims to have seen something impossible: a one-eyed, black-skinned monster direct from outer space. Gully quickly finds himself sucked into the baffling tangle of tattooed bruisers, cheerful magicians, and questionable characters who call the waterfront their home.
 
Ellery Queen is one of the world's finest detectives, but his adventures are nothing compared to the Ellery Queen Jr. Mystery Stories. Join Queen's nephew, Gully, on adventures filled with danger, suspense, and thrills.
 
The Mystery of the Merry Magician is the tenth book in the Ellery Queen Jr. Mystery Stories, but you may enjoy reading the series in any order.