When the New Bedford Whaling Museum in November announced that time slots were available to read at the annual “Moby-Dick Marathon,’’ the openings disappeared more quickly than the famed white whale did from Captain Ahab’s clutches.

Within an hour, around 150 people had secured opportunities to read from the classic novel at the Jan. 9, event, which is now in its 20th year. An additional 180 people put their names on a waiting list. Even more are expected to attend just to listen and read along or ramble through the museum’s galleries.

“You will see many people who are on the waiting list just hoping that someone’s car breaks down, or that they couldn’t make it for one reason or another. And they are ready to fill that spot,’’ said James Russell,museum chief executive.

“It has grown dramatically,’’ he said of the spectacle’s popularity.

For two decades, the museum has been celebrating Herman Melville’s literary epic by hosting the readathon, which lasts 25 hours and is fueled by caffeine and fondness for the author’s artistry.

“There’s a magical feeling about it all, particularly if there is snow on the ground and because it’s the New Year,’’ Russell said.

The location adds to the charm. A portion of Melville’s narrative is set in New Bedford, a historic whaling city. As is tradition, Mayor Jon Mitchell will read a section from Chapter 6 describing the city.

“The town itself is perhaps the dearest place to live in, in all New England,’’ a paragraph from the book reads. “It is a land of oil, true enough: but not like Canaan; a land, also, of corn and wine. The streets do not run with milk; nor in the spring-time do they pave them with fresh eggs. Yet, in spite of this, nowhere in all America will you find more patrician-like houses; parks and gardens more opulent, than in New Bedford.’’

This year is special, Russell said, because of the 20th anniversary, and new programs have been scheduled over several days at the museum.

In the days leading up to the reading, which begins at noon Saturday and concludes the following day, the museum will host an opening reception featuring Portuguese artist and photographer Nuno Sá; a Moby-Dick-inspired dinner; and a dedication of the museum’s new Herman Melville Room.

On the day of the reading, museum officials will introduce a “Children’s Moby-Dick Mini Marathon,’’ where kids can dive in and read an abridged version of the 19th-century classic for two hours.

There will also be a Moby-Dick trivia contest, opportunities to speak with Melville scholars, and a special Portuguese reading of the adaptation of “Moby-Dick.’’

Nathaniel Philbrick, author of “The Heart of the Sea: The Tragedy of the Whaleship Essex,’’ has been tapped for the most coveted reading slot at the annual gathering. The story of the Essex reportedly inspired Melville.

Philbrick will crack open “Moby-Dick’’ and bestow upon participants its most famous line: “Call me Ishmael.’’

From there, readers will come up on stage, and for 8 to 10 minutes read from the book until the last page is finished. Readings will take place in three areas of the museum, to give participants a change of scenery as the book plays out. It will begin in the Bourne Building, shift to the museum’s Seamen’s Bethel, and conclude at the Harbor View Gallery.

Readers range from children to people studying to receive their PhD’s on Melville’s writing, said Russell.

For those unable to make it to New Bedford, the event will be streamed live on the museum’s website.

The “few hardy souls that brave the voyage,’’ and are able to stay awake until the marathon comes to an end, will be given prizes, according to event organizers.

“Some come for their favorite chapters, some come for excerpts, and others stay from the beginning to the end,’’ said Russell. “It’s all about the power of the narrative, and you can lose yourself and close your eyes as you listen to people read this beautiful book.’’

Steve Annear can be reached at steve.annear@globe.com. Follow him on Twitter @steveannear.