Aaron Karo listened well in high school when English teachers gave him the age-old advice, “Write what you know.”

Writing what he knows has turned into a successful career for Karo. This year he released his first book, “Ruminations on College Life,” a compilation of humorous and satirical reflections on his four years at the University of Pennsylvania.

But how is this book different from other college books you can find in the local Barnes & Noble? According to Karo, his novel differs from others in that it was written by a college student while he was a college student.

“I didn’t write this after I graduated, like a memoir,” Karo said. “I wrote it as I was going through the four years, so this is actually what we do. When you buy the ‘Barron’s Guide,’ that’s not really what goes on — this is the real thing.”

It didn’t start out as a book, however. First, it was simply a prophetic e-mail Karo sent to about 20 high school friends one sleepless Sunday night during his freshman year. He reflected on his first month at college, giving his own honest take on dorm life, classes and, of course, partying.

Eventually, his friends forwarded the e-mail to their friends, who in turn forwarded it to more friends, and the cycle continued. Karo then began an ever-growing mailing list which featured thousands of subscribers from all over the world. Finally he put his ruminations on his website, www.aaronkaro.com, for all to see.

When he landed a book deal with Simon and Schuster last fall, Karo was faced with the task of transforming his e-mails into a book. New jokes were added and divided up into categories such as freshman year, life in the classroom and Greek life. “It was a real challenge, but I’m really thrilled with the way it came out,” he said.

Karo’s book appeals to all ages, from those reminiscing about their long-gone college days to those eager to begin the journey, but they especially ring true for students now. He describes the woes of communal bathrooms (including the “take-your-towel-off-before-you-get-in-the-shower-but-don’t-let-anyone-see-you-naked” maneuver), the truth about fraternities (detailing the rules of beer pong) and describes various campus characters you are sure to recognize (like Front Row Sitters, Slow Walkers and Friends Afraid to be Alone). He also sheds some light on the hook-up versus relationship dilemma. Also, throughout the book you’ll find insightful one-liners that will make you laugh and nod your head in recognition.

While the book might emphasize a great deal of partying, Karo claims that partying is not the only thing college students do. “I worked hard and I played hard, but playing hard is funnier. Who wants to read about studying all the time?” he said.

His accomplishments speak for themselves. Karo delivered his class speech at his 2001 graduation from the Wharton School of Business at UPenn. In July 2001, he began working in finance on Wall Street. He quit this past August to pursue his career as an author, as well as other ventures such as stand-up comedy and working on potential TV and movie adaptations of the book (which will be, he hopes, “more realistic than some of the shows on TV about college right now”).

While college might be over, that doesn’t mean that Karo has stopped ruminating. Now his website features “Ruminations” about life after college, living as a single guy in New York City. “There’s only so much you can write about frat parties, so my work has evolved,” he said. “I think that being a young, single guy in New York is hilarious; I have so much material that I could write forever.”