I would call it atmospheric.

The atmosphere is both circular logic and literary nonsense, in the tradition of Lewis Carroll’s nonsense and not the dismissive way which we say ‘nonsense’ casually.
Poison for Breakfast is not a novel. It’s a meditation on the nature of storytelling in the guise of a story.

Sort of, kind of, ‘Poison for Breakfast’ is about consuming poison and trying to work backwards to figure out how you’d gotten to the point of being poisoned. Snicket is given a note informing him that he has been poisoned and now he, as a reliably known mystery solver, must solve the mystery of this suddenly appeared note, his poisoning, and therefore his apparent murder.

He doesn’t actually tell you very much at all, buried in convoluted Lemony Snicket-ism upon Lemony Snicket-ism, meditating on the nature of storytelling. He tells various non sequiturs that he initially frames as action then admits are really just things he’s thinking about but that probably did occur at some point and therefore are still true.

Handler, as Snicket of course, talks about the nature of story structure, the importance of inspiring bewilderment, what details are and are not important to include, and the need to cause the reader to buy in to the side of the narrator. At one juncture he tells a story of a bad lesson given by an ornery writer which sounded remarkably familiar and which I paused in reading and laughed…. because I read that book this year.

Handler, as Snicket, talks about the evolution of writing advice as well, his ideas of the rules of writing changing in real time as he discusses Lemony Snicket moving about his fictional morning uncovering his potential imminent death and therefore murder.

He also very, very carefully discusses various ways to make eggs—a nod, I’d say, to the rule Lemony Snicket gives that you should only tell information relevant to the story. Handler, as Snicket, tells you many, many irrelevant things in the course of telling you the story, the story where he may presumably die at the end, without sharing other necessary information.

The true theme appears to be rules and breaking them.
Like cracking many eggs.

It is also a meditation on safety. The way in which safety can be so suddenly and irreversibly taken out from under us, “we have poisoned ourselves”.

We read to identify with bewilderment, explore our bewilderment, and we throw ourselves into imagination to find solutions to our bewilderment.

I encourage you to read this short, under 200 pages, meta narrative disguised writing advice. Slowly.

It’s in many ways life advice, too.