Learning digital photography is both fun and interesting.And if you are going to sell on eBay, Amazon or from a website, then you really need to learn how to take great photos.
As someone who was a film camera buff for years, I was late to digital photography. But, once I converted I dove in with all I had.
There is so much you can do with digital photography and these books have really helped my expand my techniques and dramatically improved my results.
These are not in any particular order. If you are a beginner, take a look at numbers 9 and 10:
Either of these will get you started with a strong foundation. The other book I really like and strongly recommend once you master the basics is number 4, The Photographer’s Eye: Composition and Design for Better Digital Photos.