Poison For Beginners is a 14 page fantasy reference on natural poisons. It's broadly intended for PbtA and d20 systems, but it contains some information that is generally useful all around for writers and roleplayers---although it's definitely not a scientific reference, and you absolutely want to double-check all of its information before using it as anything other than a cool game mechanic.
Overall, Poison has a very clear, readable layout and a cool Victorian handbook vibe, and its writing is super strong. There's also comprehensive, useful information on a variety of naturally growing poisons that can be found in (I think) primarily northern climates.
Not everything has an illustration, so I wouldn't treat this as a handbook for going out and ID-ing stuff in the wild (although just knowing that False Morels exist can potentially save your life if you're idly mushroom hunting---btw, on that note, never consume anything you can't 100% beyond-all-possible-doubt identify.)
Also, not everything has all possible names listed, so it's possible you might know a thing by a term that isn't in the pdf.
Also some poisons have been fantasticized, for example the Calabar Bean, which in real life just kills you instead of mildly punishing you for lying, or the Destroying Angel, which the game links to an actual destroying angel, or the False Morel, which again just kills you irl instead of making people not believe you.
Overall, it felt a little strange to me that the book focused so hard on taking real herbs and then adding fantasy effects to them, when it could have just as easily have come up with fantasy herbs and had a little more leeway to assign traits to them, but at the same time it's a cool toolkit and has good information about various ways poison can be prepared, how settings handle the existence of poison, and some examples of how to GM situations involving poisons.