Overall, "Not a Drop to Drink" was a pretty good read. I particularly enjoyed the survivalist portions of the book. Not being an outdoorsy person myself, I know next to nothing about any kind of water purification, hunting, tracking, etc. so I cannot speak to its accuracy, but it was still interesting.
I guess my only issue with the book was that I constantly was wanting more details about, well, everything really. I wanted more information about the water shortage, more information about the government, etc. and all we really got was a very quick, high level overview of the situation. I wanted more depth to the characters (and less characters with similar-sounding names, so confusing!), because aside from the main character (Lynn) I didn't really feel connected to any of the side characters at all.
My favorite aspect of the story was the fact that the characters all had what I would consider realistic, if a little depressing, fates. This kind of honesty was kind of surprising given this is a YA book, but the darkness was wonderfully effective. In real life not everyone is going to survive. The good guy does not always win. This fact would be particularly true in a time of crisis, as this book showcases particularly well. My only exception to this praise would be the overall ending of the book. It just did not feel realistic to me, simply due to basic human nature. I cannot really get into more details without spoilers, so I will just leave it at that.
If you enjoy dark, survivalist reads with a little romance and a whole lot of sadness, you should definitely pick up this book.