For five years, Katherine Ramsland, an author and associate professor of forensic psychology at DeSales University, has been talking to Dennis Rader, the BTK killer.

From 1974 to 1991, Rader killed 10 people in Segwick County, Kansas, but he wasn't caught until 2005.

There have been many books about Rader and the investigation into his crimes, but Ramsland wanted to go deeper.

"For me to be involved, I had to make this something that would benefit my colleagues, my discipline and also the things that I teach to law enforcement," said Ramsland.

Ramsland said "Confession of Serial Killer" is a guided autobiography of how Rader believes he became a serial killer, starting with an early fascination with killing animals and coveting the notoriety of serial killers who tied up their victims.

Ramsland said killing became a sexualized addiction for Rader, who initially would only share the inner-workings of his mind in cryptic hand-written codes.

"He thought of himself as a spy. It's kind of a little play-acting thing that he did, so the codes satisfied him on that level and they also created a threshold for me," said Ramsland.

Ramsland said Rader also spoke about the 14 years between the last murder and his capture.

"He sent me a list of 55 projects that, he said, 'If all of these people would have come home, I was in their house waiting for them. I had stalked them. I had planned. I had dug graves. I had all kinds of plans, but those things didn't work out,'" said Ramsland.

Ramsland said the families of Rader's victims will receive most of the proceeds from the book.

She said they're not happy he is back in the limelight, but understand it could help mental health and law enforcement officials better understand the mind of a serial killer.

This is the 58th book written by Ramsland.