Around a year ago, we started following the fortunes of a pair of young East Bay entrepreneurs–Eva Sasson and Justin Mardjuki–as they launched their company, TappMob, run by college students, for college students.

Earlier this week, I caught up with them just as they were about to return for their junior years at Barnard College (Columbia), and the Wharton School (Penn).

They’ve expanded their team to “around fifteen” at colleges around the country, including Stanford and U-C, Berkeley, and have just launched a new product, TappBooks.

The idea behind TappBooks is to address the glaring disparity in how much college textbooks cost students to buy at the beginning of a semester, compared to how little they get back when they try to sell them at the end of the semester.

“It's a huge ordeal at the beginning and end of every semester,” said Mardjuki, COO of TappMob. “Campus bookstores sell them at a huge markup and then buy them back for twenty cents on the dollar.”

To use the free app, which just became available in the iTunes Store in time for the beginning of classes this fall, students sign in with their Facebook IDs, and then can locate others on their campus who want to buy or sell the textbooks required for their new set of courses.

Utilizing the Google Books API, TappBooks displays the average price paid online for the books in question, which will normally be well below what the bookstore charges, and well above what the bookstore buys them back for – a win-win for the students on either end of the deal.

This is essentially a new p2p marketplace for college students.

“Because we are all students ourselves, we know what we want and need,” says Emily Hsia, TappMob’s V-P, Engineering, who also joined us at our recent meeting in a Mission District café.

“We want to build out a library of apps for college students -- things that will affect our everyday lives in various ways,” says Sasson, CEO of TappMob.

As they do so, these students are learning on the job. One member of their team had never built a server before when he took on that task, soon after taking a class in databases at Columbia.

“When I started here, I didn't know how to write in html, CSS or Javascript,” says Hsia. She does now.

In order to market their products on campuses, TappMob has established a “campus founders” program, whereby student ambassadors use guerrilla-marketing techniques to spread the word on their campuses.

TappBooks is launching via these founders on an initial set of twelve campuses this fall.

“We give them flyers, sunglasses, they set up their own events,” says Mardjuki.

The founders, like the staff members, are not paid salaries – the financial incentive is equity in the young company.

“Because we are all in touch, we get lots of feedback from each other, and exchange ideas about what works and doesn’t work,” says Sasson. “One of the reasons people are so excited to be working with us is that we are all learning from each other -- from our peers.”

One common trait shared by Sasson, Mardjuki, Hsia and most of the other key members of their team is that they are all children of entrepreneurs – mostly their fathers.

In this way, launching an innovative company of their peers almost seems baked into their corporate and personal DNA.

One update from the piece I wrote last year about them. Their very first app, Check-In, is no longer in the app store as they’ve pulled it back to retool it especially toward the needs of college students.

“We are focused strictly on the college student market, and products students can use right now, says Sasson.

When I asked how they maintain a balance between attending to their academic work and running their company, Sasson laughed.

“School always comes first for us. We all make sure to note for each other when our finals, midterms and study days are, and then we serve notice ‘Don't Contact Me’ on those days.

“We are students first.”

BTW, our ebook, 30 Startups to Know Now, is available on Kindles.