I rediscovered Jaime Retief in my fifties and recommend it highly to older adults.
Great juvenile Sci Fi holds up well, as a rule.
As a child I enjoyed the action and thought the "professional" behavior of the characters silly.
But now, I've dealt with so many Pouncetrifles, Dimplicks, and Groaci and Boge, over the years that it's the broad exposition of the "professional" behavior of the characters that I most enjoy.
Even as a kid I recognized and enjoyed the caricatures of government bureaucrats. To a kid who grew up during the height of the Cold War it was a breath of fresh air.