This is not in any way a complaint. The Booking.com site says there is a shuttle from the airport and we almost were caught out by this, expecting a shuttle bus. However what we had to do was to get a taxi and then the hotel paid the driver. Clients might want to check this out.
We booked a family room, which was actually two spacious rooms with a large bathroom, with bath. Everything very warm, clean and comfortable. The children loved it! They loved the breakfast even more. The food choice was very wide and plentiful, with lots of smoked salmon, all the usual breakfast foods, and several choices of good cake. Coffee, hot chocolate and other drinks are always available, free of charge, from the sitting area near the lobby. We have stayed elsewhere in Keflavik but in future would stay only at the Hotel Keflavik. For what we got, the value was superb.