[lcall]

A few books I read or am reading now, though I'm not in business or management currently:

The Personal MBA: master the art of business, by Josh Kaufman (and personalmba.com has more info, maybe). Seems to want to be the practical guide.

MBA in a Nutshell, by Milo Sobel. Seems slightly more academic than the one just above.

Start Your Own Business: the only startup book you'll ever need, from Entrepreneur

At least the first two come with lists of recommended further reading, by topic, including on finance, marketing, etc etc.