Mark Vonnegut gave the speech on his late father's behalf

The lecture - written two weeks before the author's death aged 84 earlier this month - was delivered by his son Mark.

Vonnegut had planned to present it himself, as part of a series of events held to honour him in his home city.

The writer's most famous works are Slaughterhouse-Five and Cat's Cradle, which became cult classics with students in the 1960s and 70s.

Time capsule

Mark Vonnegut said the sold-out event was "a great honour to him".

"I'm trying to figure out if he's sorry he's not here or not. He was really, really serious about being funny," he added.

Vonnegut served in the US army during World War II

Vonnegut interview

The speech concluded with the line: "I thank you for your attention and I'm outta here."

The Year of Vonnegut in Indianapolis was designed to encourage more people to use libraries.

A number of items, including a copy of Slaughterhouse-Five, have been placed in a time capsule which has been sealed for 50 years inside the city's newly-expanded main library.

His final book was A Man Without A Country (2005), which was published in paperback at the beginning of this year.