"And besides, libraries are also all about promoting lively discussion, so why not get in a psychologist who is an expert on casual sex?"
The festival opened with a screening and discussion of Steve McQueen's Shame, a film about sex addiction, and a discussion with psychologist Dr Pani Farvid.
Other events include a panel with comic artists Dylan Horrocks and Sam Orchard on how erotica has changed in the 21st century.
For the finale, the Grey Lynn Library hall will hold readings of erotic literature, music, burlesque and theatre exploring the theme, including opera/burlesque troupe Oh! Is For Opera.
Co-organiser Tosca Waerea, Auckland Libraries social media coordinator, wants to use the festival to develop the libraries' relationship with its lesbian, gay, bisexual, and transgender users.
"Very often, at certain times of the year, we celebrate a particular thing, in this case, sexuality," she said.
"But for our LGBT customer, that's an identity they wear every day, and we don't do a lot that addresses that."
Waitemata local board member Tricia Reade said that attracting an audience in the 18 to 25-year-old group was important as libraries had seen a drop, and issues surrounding sexuality were high on the agenda after the recent passing of the Marriage Equality Bill.
"There may be people that question the value of it," she said.
"But what Dark Night is doing is looking at questions of sex, sexuality, and even pornography. If we don't have open and honest discussions about those things, we're making it even more sleazy ...
"I should imagine for most people it's going to be terribly informative."