A little shallow

Interesting book about the history and use of different poisons, mixed with stories of how famous people died by poison through the years. I absolutely loved the ancient Greek and Roman cases but the book also focuses on very recent poisonings.
The book did feel a bit shallow sometimes as it just states basic facts, it doesn't feel like the author took a deep dive into the matter but more just stated basic facts.
The fact that the book just stops after the last case took me by surprise. Except for an index, there was no closing text or word from the author about his research or why he decided to write this book.