We’ll have to wait until all the holiday sales are added up to know for sure, but it’s a good guess that digital books accounted for roughly ten percent of all book sales in 2010 --a remarkable figure that will only be going up in the future.

And it’s no surprise that several innovative Bay Area companies are in the thick of the action.

From an office in SOMA, Scribd has emerged as a leader in “social publishing” by making content easily shared via Twitter, Facebook, and blogs.

Since its founding in 2007, Scribd has aggregated more than ten million digital books, and according to Quantcast, attracts over 40 million readers per month.

Another aggressive local player in the digital publishing industry is Smashwords, headquartered in Los Gatos, which since its launch in 2008 has helped indie authors publish and distribute over 25,000 e-books.  

At Smashwords, authors and publishers retain full control over how their works are published, sampled, priced and sold. It serves as a virtual playground for readers, since you can read up to half of most of the books that are for sale there.

The company notes that “(I)f an author wants to charge one dollar or ten thousand dollars, or give it away for free, they have that freedom.” 

Earlier this week, Smashwords founder Mark Coker predicted that “Ebooks sales will approach 20% of trade book revenues on a monthly basis by the end of 2011 in the US” – and account for at least a third of those books that actually get read.

Beyond startups like Scribd and Smashwords, the Bay Area is also home to thegorilla in the attic of the eBook industry: Mountainview-based Google.

The search giant shook the digital publishing community to its core earlier this month, when it launched its electronic-book store offering titles in almost every browser or mobile platform except for Amazon's Kindle device.

Even before taking on Amazon directly, Google had already staked its claim to the future of eBooks with its gigantic book-scanning project, which aims to turn every book ever published into digital form to reside in the world’s largest virtual library, which will double as a bookstore.

That effort has been tied up in a class-action lawsuit that awaits a federal judge’s ruling in New York. As I explained in a post earlier this year, what is at stake in the Google Book case is nothing less than our access to our pre-digital history.

It now seems likely that a ruling in that case will come early in 2011 -- a decision that one way or the other will likely accelerate the transition to digital publishing in the future.