It depends on your playing strength and your use of the product. The best product is both used together.
Books or Computer Software ?

some do well with books, others with videos. i tend to learn much faster watching videos, so they work for me. i have quite a few books, though; you can never get too much chess information. :)
if you get Fritz, you can kill both those birds with one stone, as it plays chess DVDs as well. also, the videos here on chess.com (for paying members) are top-notch. i'm loving them.
I am a chess player who would like to know what is the best training method, is it by reading, and studying books, or by buying some computer chess software that will train you. Or are they both equally good just depending on your chess skill ?