I read this book 15 or so years ago and can't remember the title, although I think it had the word "Paradise" in it. It took place in the future and centered around a man who lived in a giant hotel along with other people. The different floors had societies but massive sections of it were uninhabited. He eventually makes his way into the "Lagoon Room" and lives there for a while. At some point he visits the Penthouse where a "wizard" lives. He also ends up in the basement at some point where there is a sentient computer. At the end he makes it to the Lobby and goes outside and sees another giant hotel across the way and has a conversation with a man outside. He convinces him that they aren't actually outside, they are in a huge room inside yet another hotel.
Other random things I remember is that the birds and fish are mechanical and say jingles for products he has never seen like mouthwash. He sees mouthwash in the lobby and, not knowing its function, drinks it. These robots are frequently spying for either the wizard or the computer.
He has a "tab" at a bistro where he gets food. It is made from soy or something similar because they are always out of "real" food.
He spends the night in an empty hotel room and watches the snow on the TV screen.
There are giant cracks through the hotel. A robot that is chasing him gets dragged into one by a woman who is helping him.
He has all his teeth pulled by a robot in the Lagoon room as a sort of trial by pain. They are then replaced with new teeth.