The author literally labeled that room the "Upstairs Office".
The rest of the house (kitchen, living room, etc) that's not dedicated to LAN computers looks like a normal Euro/Scandinavian type of clean minimalism aesthetic which a lot of people like.
My home currently has a lot of "traditional" style furniture and decorations hanging on the walls which some might call "warm & cozy". But others would disagree and think of it as "grandma's house" and as I've aged, I tend to agree. I'd like to eventually dial it back and redo the interior to be more minimalistic but I have other higher priorities than remodeling the house.