Learning about business is probably a good idea for anyone who works for a living, and possibly others.
I decided to this recently and went back and forth with the idea of going for an MBA, but realized that the return on my investment of money and time to get it would not be worth it, so I decided to learn on my own.
The first book that I'm reading for that purpose, and I'm glad that it is, is "The Personal MBA: Master The Art of Business" by Josh Kaufman. This has been excellent so far, giving a concise introduction from scratch to what seems to me like a complete A to Z of business topics, and providing pointers to where to learn more. The writing is clear, and I have actually been enjoying reading it.
After reading that, you can branch out into more specialized books on topics about which you would like to learn more. The author of the book above has read thousands of books on business and other related topics and points you to the ones that he believes are worth your time.
Good luck!