Books about speakeasies which structures still exist today. I use to watch a show on the history channel called... underground cities (????); I just found it so damn fascinating. They went down into Al Capone's speakeasy in Chicago, and because the next door had demolished most of it at some time, the only thing that was left was old urinals. It was below a pub.
I know what you mean - structures that are still standing that were speakeasies back in the day.
This isn't a book, but it's a website:
Visit Prohibition-era Speakeasies.
It leans toward Chicago & NYC, which isn't much of a stretch in my mind (by that I mean, doesn't it just figure those are the 2 cities which would have the most intact speakeasies?).
ETA: I also second Medievalist. This, from the comments at Amazon about Last Call:
"In spite of the language used (you may need a dictionary to decipher some of the words that are no longer in common usage)this book isn't as dry as its topic suggests." My reasoning is that if you're going to write a novel about this period - and speakeasies in general - you might want to get the venacular (sp?) right.
I also found
this book on Prohibition and speakeasies in Manhattan. I don't know if it has exactly what you're looking for, but it might help as to where speakeasies were (or are still) located.
I enjoyed the Underground Cities (or was it Cities Underground? Can't remember) series on the History Channel, too.
Good luck!
Nancy