Realizing that books are in rare cases better heard than seen, (NASDAQ:AMZN) is acquiring audiobooks publisher Brilliance Audio. It's an intriguing move, considering that Amazon hasn't been buying hardcover houses or major record labels to shore up its media retailing elsewhere. But snapping up the country's largest audiobooks-only publisher will take Amazon one step deeper into the distribution process.

It will also likely bring Amazon one step closer to partner Audible (NASDAQ:ADBL), which thrives on the digital delivery of spoken-word content. Audible and Amazon have been buddies for a while now.

" is our trusted partner for audio download programs and players, and we hope that you'll find their site as informative, fun, and easy to shop at as you find ours," reads Amazon's page pitching its audio downloads.

Amazon has eight "trusted partners" like Fidelity Investments and Shutterfly (NASDAQ:SFLY). However, it's has never hinted at moving into selling mutual funds or printing photos of your rowdy Caribbean cruise. Weight Watchers (NYSE:WTW) is another partner, and the only kind of weight loss that Amazon is interested in is making your wallet a little lighter at the other end of the checkout screen.

Digital delivery is different. Between last year's launch of Amazon Unbox and the upcoming MP3 music store, it's really just a matter of time before Amazon starts selling digital audiobooks in a much bolder way than its low-key CustomFlix on-demand service does.

Maybe I'm wrong. Maybe Amazon will simply feed Audible top-shelf content and keep this symbiotic relationship going. However, now that Amazon is beefing up its audiobook catalog, the next step is to either compete with Audible or to buy it out.

That has to be the next chapter. Either that, or I'm just listening to all the wrong audiobooks.

For related Foolishness: is a Motley Fool Stock Advisor selection. Want the next chapter for free? Go for a free 30-day trial subscription.

Longtime Fool contributor Rick Munarriz has always felt that it's a matter of time before Amazon takes on Audible. He does not own shares in any of the companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.