Though they may only account for a single-digit portion of the overall book market at present, sales of ebooks are soaring globally and will probably reach $12.7 billion (16.1 percent of all book sales), according to Outsell, by 2013.

And since Amazon has established that there is a “long tail” for physical books, that should logically be even more true for ebooks.

After all, digital technologies from search engines to social media sites to e-reading platforms just naturally seem to help people with similar interests and needs connect with one another, as well as for niche products to find their markets.

Into this very space comes an intriguing San Francisco startup, Hyperink, which publishes short, high-quality ebooks mainly, for now, in the “How To” category.

Thus among its first 100 or so titles are How to Start a Mommy Blog, and Patenting Your Start-Up Idea, and Having Great Married Sex.

“We are building a company that helps people share knowledge online and make a living at it,” says co-founder Kevin Gao. “We want to work with millions of experts, helping them publish beautiful high-quality ebooks.”

There is an old cliché that anyone can write a book, which is not true, but since Hyperink employs journalists to work with its authors as ghostwriters, anyone really can write a book in this case.

Gao contrasts his company’s approach to publishing with the mainstream publishing industry, which traditionally churns out long books that take a lot of time and money to produce and are therefore geared toward the largest possible audience.

“We’re a lot more specific and our books are a lot shorter, about 10-20,000 words each,” he explains. “Rather than publishing a book called ‘Getting into College,’ we’ll publish ‘Getting into Cornell,’ for example.”

Like most smart digital tech companies, Hyperink has developed an algorithm to help it understand the “demand-driven” market for new titles. That algorithm considers trends among online search terms, as well as existing book sales, and the kinds of questions people pose at various online sites.

“There are lots of different signals we gather,” says Gao, noting that among the data his team values the most are which titles sell well for Amazon’s Kindles, and Barnes & Noble’s Nook devices.

Hyperink publishes in all the major digital formats, including Mobe for Kindles, Nook, the iBook Store, epub, PDF, with the exception of a few like Kobo, which they intend to support soon.

The company prides itself on a fast turnaround time, from two to six weeks from the date of receiving a manuscript to publication of the ebook.

The royalty formula for authors ranges up to 50 percent, with a lower cut when collaborating with a ghostwriter (perhaps 25 percent each in that case).

Hyperink sells the books through its website but also pushes them aggressively over social media networks. “That has to be driven by the author to be effective, but we can help them with that,” Gao explains.

The Y Combinator graduate from last winter’s class has raised a $1.2 million round from blue-chip investors and currently employs six people at its Bryant Street office. As to how many books he expects to be able to publish in the future, Gao smiles and says, “Everyone is an expert at something.”