I spent 2 nights here, in the "Adam Hotel" part, I think. At least , this name was on the reservation which was made via eBookers. There is also a "Adam Guesthouse" part, and most of the reviews seem to describe this part.
The location is very good, very close to the Hallgrim's Church and having a supermarket on the ground floor.
The entrance is NOT from the gate given in the address, but from a parallel gate. There is no reception, but there was a guy sitting outside the house who provided me with a key.
The room was not superb, but ok, with 2 twin beds. There was a little kitchen section which I did'nt use. The batchroom was a challenge: The water was accumulating on the floor just inside the bathroom door, and the shower curtain was a bit temporary and falled down the first time I touched it.....
When I left the hotel 7.30 a.m to reach the airport bus, I couldn't find anyone to give the key to. So I just left the hotel keeping the key in the room door....
But anyway, I nearly wasn't at the hotel and it was ok for 2 short nights. I wouldn't recommend it for a longer stay.

I'm still laughing about all the other reviews and how they all describe the owner of this hotel. It is true, he has an attitud and the first thing he is going to ask you is to pay, pay, pay! After that, he will take you to your room, or what can better be described as a closset. We booked a double ensuit and got 2 tiny little beds, a sink with some plates and utensils, a tv and a desk that if you use it blocks the entrance. The bathroom is made for elves! You can even move once you are in it. It also smelled really bad ( hot water in Iceland smells like rotten eggs because of the sulfur but only whe you use the hot water) this bathroom smelled like this all the time. If you want to be in the center of town and just need to crash somewhere for 1 night, stay here. Otherwise go somewhere else.

I stayed there a while ago, but have just recently registered with trip advisor and am leaving reports for a couple of hotels I felt strongly about in the past (both positive and negative). The location of this place is great, but everything else is awful. I was promised an en suite bathroom and instead had a shared bath. the owner had the nerve to tell me that "ensuite means shared in Iceland". Absolutely ridiculous, and the room and shared bath were both dirty and dingy. He was extraordinarily rude, and, I would even say, mocking, throughout my stay. He also refused to take a message when a rafting outfitter called to leave a message for me. The rafting outfitter actually complained to me about how rude he was and said they've had trouble with him before. I missed going on a trip as a result. It would be much better to stay at a hostel or spend a little more on a nicer place. Don't even consider staying there if the ownership hasn't changed. As it was, this was no bargain.

Guesthouse AdaM is situated at realy nice location in Downtown Reykjavik. But this is the only good thing! It was very dificult to find the entrance, because it is not actualy at the Skolavordustigur street. By the entrance to the guesthouse was a mess and big hole full of trash and other stuff. Rooms are nice, but the service of this guesthouse is terrible (owner)! He was annoying, arrogant and absolutely without interest in his guests. There is a lot of hotels and guesthouses in that area, so why go to the worst one?! Never again!