What’s on your summer reading list? For more than 30 people who came to the Peabody Institute Library on a recent July evening, it’s Walt Whitman’s “Leaves of Grass.” The book of poetry is an American classic, but it’s not your typical light beach fare.

Nevertheless, excitement was in the air as people filed into the historic Sutton Room, awaiting the arrival of Theo Theoharis, an associate in the comparative literature department at Harvard University, who is leading a four-part series on Whitman’s magnum opus.

“I see a lot of people I know,” he said, surveying the crowd and recognizing familiar faces from the two previous series he presented on Herman Melville’s “Moby-Dick” and Dostoyevsky’s “Crime and Punishment.”

Theoharis has been a driving force behind the success of the library’s summer events for adults, according to adult services librarian Kelley Rae Unger. “Since we’ve had Theo here, the program has really grown,” she said. “At the average lecture we’re seeing around 40 people. I’m thrilled.”

Peabody resident Bridget Keown has attended all of Theoharis’s programs at the library, including the one on “Moby-Dick.’’

“It was really just an eye-opening experience,” she said. “We’d talk about the same scene a few times and every time there was something I took away from it that I hadn’t before considered. It becomes more than just a reading experience. It’s a learning experience that you carry with you into everything you read.”

Al Hayden of Danvers is also a fan and has been looking forward to the Whitman series.

“After having gone to the first two, I just think he’s such a wonderful teacher and lecturer. I couldn’t miss out on it.”

To open the discussion about Whitman, Theoharis threw out a few questions:

“How many of you have never read Whitman before?”

“How many of you have a great enthusiasm for Whitman?”

“How many of you have read Whitman in the last five years?”

The show of hands after each inquiry led him to remark, “All of that tells me Whitman is still a living writer.”

That gets to the crux of what Theoharis aims to do, and one of the reasons he enjoys leading groups outside of a university setting.

“Somebody in a group like this might ask, why should we put up with the difficulty or the obscurity of parts of ‘Moby-Dick.’ Nobody in college would ask that,” he said. “With a mixed adult audience, you can’t simply ride on the presumed value of the work. You have to show the relationship of the work to the lives of the audience much more explicitly.”

Genevieve Gilson of Peabody, another regular at Theoharis’s programs, appreciates that. “I think he has a magic bow tie,” she joked, referring to his customary choice of neckwear, then continued in a more serious vein. “He has a wonderful ability to take things that are not necessarily accessible at first glance and point out the connections to the present day.”

That ability was apparent in Theoharis’s remarks on Whitman’s views of the “common man.” “Your commonness is something that happens to you and something you do,” he said. “It happens to you when you accidentally discover the value of a friendship. You do it when you end a love affair.” Poetry to Whitman, he continued, is both something that happens to him and something he does.

Theoharis also engaged the audience, encouraging questions and comments. When participants contributed to the discussion, he addressed them by name, demonstrating personal warmth and a knack for connecting people through literature.

“It’s one thing to sit alone in your house or on vacation and read a book, but there’s also something to having a community around a common series of ideas,” said Hayden, who has made several friends through the library’s programs. “I think there’s a sense of community that even with blogs and Twitter and all of that stuff, technology just can’t replace.”

Unger said that since many people did not read much in high school or college, “these programs give them an opportunity to read those books and discuss them with other people.”

Says Theoharis: “The physical delivery of books is in flux right now, and that means to some extent the culture of reading is in flux. But I don’t think the need to read or the pleasure of reading is endangered by that fact.”

After 90 minutes of lively discussion about Whitman that showed no signs of slowing down, Unger signaled from the back of the room in what has become a common occurrence at Theoharis’s lectures.

“Theo, the library is closing,” she said. The disappointed crowd gathered their belongings and prepared to leave, clustering in small groups to continue the conversation as they walked out, lingering on the sidewalk to ask just one more question, make just one more point, before going home to think, ponder, and read the next installment.