Neverwhere [Book] Question [Spoiler Warning]

[yomom1919]

Tiny spoiler warning:

 

 

 

I have a question about the book Neverwhere. I just finished reading it and its been bothering me, because I'm not exactly sure about something. Maybe I'm missing something, but is there actually a mystical 'London Underground' [in the book, I know theres one in real life, well a non-mystical one anyway], and did all these events actually happen? Or is it all a result of a breakdown or dream of some sort? I can't tell if he's just gone crazy or not at the end either.

 

Any theories/explanations are appreciated.