I was a kid when this series came out, so a lot of the drama and character interaction was lost on me at the time. I have found the DVDs though, and have subsequently enjoyed the series again.
However, back in college, I did read the book the series is based on and found it to be one of the best modern, urban, non-fiction reads out there. If you are a fan of the TV series, you should certainly try the book. Most of the stories in the book were directly translated into TV series episodes or subplots.
The author, David Simon, did an amazing job with his writing. He spent a year with the Baltimore Homicide Division from I believe 1987-88. The book is about that year he observed as he rode along with the detectives. Everything from race relations and city politics, autopsies and interrogations, 'old school' policing vs community policing, it is in there. While it might seem a little dated now, it is still worth the read.
I still love the story about the photocopier being used as a polograph on one of the suspects!
Noah