The Cat Who...

The Cat Who... is a series of twenty-nine mystery novels and three related collections by Lilian Jackson Braun and published by G. P. Putnam's Sons, featuring a reporter named Jim Qwilleran and his Siamese cats, Kao K'o-Kung (Koko for short) and Yum Yum.

A thirtieth novel, originally announced for 2008, was postponed indefinitely by its publisher and then canceled after the author's death in 2011.

[1] James Mackintosh Qwilleran is the main human character in the books.

Qwilleran (Qwill to his friends) is a man who goes from late forties to mid fifties over the course of the series.

"Kao K’o-Kung" is the full name of the Siamese cat who is almost always referred to as Koko.