It seems to me that there are two ways to go. First, a compendium of simple recipes (say, The Joy of Cooking), or something that will actually teach them the whys and wherefores. For the latter I would suggest Alton Brown's I'm Only Here For the Food. His few pages on roasting meat (for example) and how the heat actually penetrates will automatically make you a better cook if that's something you didn't already know.
It all depends on whether you think the recipient will sit down and read the book, or simply use it as a reference when the need arises.
