Guthrie joined the Royals on a free transfer from Saturday's Barclays Premier League opponents Newcastle in July.
The 25-year-old midfielder was impressed by McDermott's determination to lure him to Madejski Stadium.
"I was in the last year of my contract and there were numerous meetings between my agent and Newcastle," he said.
"We couldn't agree on anything and I was talking to a number of clubs.
"The manager came to see me while I was on honeymoon in Dubai and when I came back I'd signed.
"I was fine with him coming during my honeymoon. It was surprising and a nice gesture. It showed intent.
"I mentioned it to my wife Rebecca and she was glad to get rid of me because we were coming to the end of the holiday! It went down well.
"Once I met him and listened to what he wanted to do, it was just a case of me getting home and signing the papers."
Guthrie enjoyed his time St James' Park, but realised his days were numbered under manager Alan Pardew.
"I had four good years at Newcastle. It was bit of a rollercoaster with five managers, but the last couple of years were good," he said.
"We had a great season last season and I have nothing but good things to say about the club.
"I had a period last season just after Christmas where I was playing some of the best football of my career.
"But one of the lads came back from injury and went straight back into the team.
"That was difficult to take, very frustrating, and that's one of the reasons I left.
"The manager was honest with me, we tried to agree on a contract but it wasn't going to happen."
Reading sit bottom of the Premier League after securing just one point from their first four matches and Guthrie would like their first victory to come at the expense of Newcastle.
"I'd like to get that win because we need it, but it would be sweeter to get it over your old team, everyone would agree with that," he said.