I'm a reader of both fiction and non-fiction, and I usually have one of each going at the same time. However, I know that not everyone enjoys reading non-fiction, and understandably so. The purpose and delivery are often so different from that of fiction, that it's hard to appreciate when you're not used to it. It's hard enough going between different genres of fiction, and it's an even greater leap to cross the fiction/non-fiction barrier.
This book reads just like a novel, but another reason I think it's a good first step towards non fiction is its great potential for pointing you in a new direction of interest. Part of the reason non-fiction can be so intimidating is the wide array of topics and the diverse levels of detail within those topics that are available to you. After reading The Poisoner's Handbook, you may discover you have an interest in poisons, or ever chemistry in general. You may also be drawn in by the history and find yourself wanting to know more about The Prohibition. The possibilites are endless, but at the very least, you will have walked away with a pleasant first encounter with non-fiction.
I do hope you pick this book up and give it a try. If you do, come back and let me know how it went!
Love and (a book) light,