I strongly suggest Elaine Cunningham's books of which many are set in and around Waterdeep:
The Dream Spheres
They're some of the best D&D books, IMO.
Good list, with the exception of Thornhold, which is a complete mess of a book with a terrible, unconclusive ending due to circumstances beyond Elaine Cunningham's control (of whom I'm a big fan). An Amazon review has a good explanation of what happened with this story:
This book puzzled me, so I took the author up on her offer and emailed with questions. She admitted that the story was not supposed to be the END of the Harper series, but a PIVOT that would end the numbered SERIES but would take the Harper organization in new directions. The Harpers have changed before, and a new upheaval was planned. The characters introduced in this book would continue, and a lot of the plot threads would resolve. She especially wanted to see the Algorind young paladin overcome the betrayal he suffered without losing his faith, and "move from unquestioning acceptance into true wisdom," was I think the words she used.
So what happened? TSR abandoned the plot line and decided to move in completely new directions. The book was changed from a pivot story and put out as the last book. Cunningham admits that if she had known this was going to happen, she would have written a very different story, because this one sure doesn't END the Harpers. It wasn't meant to. The ending as written, and as the situation stands, is not very satisfying.