The Thin Man is both a novel and a film and the one is as enjoyable as the other.
The novel was written by Dashiell Hammett (1894-1961) - it was the last of five thrillers he wrote, in 1934, and stands apart from the rest for not being hard-boiled but rather a drawing room comedy with dead bodies. The main characters are Nick Charles, a former detective who is seldom without a drink in his hand, and his clever young wife, Nora, a wealthy socialite. Nick has stopped working to take care of his wife's fortune and spends most of his time getting cheerfully drunk. The novel is set in the period the U.S. suffered under the Prohibition (1919-1933), but that doesn't seem to be a problem for Nick, for there is always enough alcohol, for example in swanky speakeasies.
Unless you like puzzles (which I don't) the plot is of little consequence - interesting are the witty dialogues between Nick and Nora and the bantering detective duo that is "playfully in love" eventually became a media archetype. The two characters are thought to have been based on Hammett and his longtime girlfriend Lillian Hellman. A reluctant Nick is dragged into solving a sensational murder involving the weird Wynant family and various gangsters, all the time cheered on by the thrill-loving Nora.
The fun of the book is even heighthened in the film made in 1934 by W.S. van Dyke, for there is real chemistry between Nick and Nora as played by William Powell (of My Man Godfrey fame) and Myrna Loy. They often seem to be improvising just for the fun of it.
Not surprisingly, the film became a wild success and was followed by five sequels, between 1936 and 1947, all in the same vein, although no longer based on a story by Dashiell Hammett. Powell and Loy played their screen marriage so naturally that people mistakenly thought they were a couple in real life as well. They revolutionized the portrayal of marriage in films, doing away with its virtuous and staid image and making marriage sexy. Of course, they have a dog (Asta) rather than kids, a dog which actually plays an integral - and humorous - part in solving the various mysteries.
P.S. the five sequels of the film are: After the Thin Man (1936), Another Thin Man (1939), Shadow of the Thin Man (1941), The Thin Man Goes Home (1945) and Song of the Thin Man (1947). They are all hugely enjoyable, but After the Thin Man is probably the best. See a review of all six films in DVD-Talk.