Up until 2001 you could. That's when my book publisher declared bankruptcy and wouldn't revert rights to me (despite such a clause being in the contract). The short story is that I had an active Web site at the time in support of my work, so I tried direct selling to customers. It worked better than using a large traditional publisher, as it turned out. My eBooks got to market faster and returned a better income to me. For niche market products like mine, direct sales simply work better.