Zoe Schlanger - The Light Eaters. Buy this yesterday. It's so fucking good. All the current science on plant communication and neurology. The Factually podcast did a good interview with the author recently- https://www.youtube.com/watch?v=eBToVPeuHX0

Michael Pollan - The Botany of Desire. Pollan is better known for his How to Change Your Mind book about psychedelics, but this a particularly good book on four materialist histories of plants.

Matt Candeias - In Defense of Plants. It's kind of like a broader version of The Light Eaters with a focus on plant behaviour.

Richard Lewontin - The Dialectical Biologist. This and Biology as Ideology did more for me as a scientific horticulturist than any particular book about plants. To understand a plant, you need to understand the dialectic of organism and environment because a plant is intrinsically tied to one setting it mediates its whole existence around. The biggest thing that will hinder you in plant science is the way it isolates the subject into an object of study, trying to remove as many of the variables as possible. But plants exist as a product of endless variables and The Light Eaters shows that we've barely scratched the surface of their world or how it works. The more nuance you can build into how you approach plants- the ecology, the chemistry, the soil-atmospheric interfaces, the ethnobotany and anthropology, the environmentalist theory- the better you'll understand them. Botany on its own is pretty narrow.

You can start learning about plants by making use of local field guides. In the EU we have Collin's guides (Tree Guide, Wild Flower). I can also recommend "Identification of Trees and Shrubs in Winter Using Buds and Twigs" by Bernd Schulz which has beautiful illustrations of the details of the twigs and buds of plants during winter, and so it is great for learning to identify trees when they lack leaves. This book is also EU-centered. If you would like a technical book to get really into evolution and taxonomy of plants, I can recommend Plant Systematics by Michael G. Simpson, which is quite good! This one covers plants from around the entire world, but it is not light reading.

For plant nutrition, I read "Soil Science for Gardeners" by Robert Pavlis before I bought the more technical plant nutrition one. Robert Pavlis is the author of a website about gardening myths (https://www.gardenmyths.com/) and he has some books about compost and plant science. I have only read the Soil Science one and it is good. It covers the structure of different types of soil, how nutrients stick to and are release from soil grains as a function of factors such as acidity, the structure of roots, etc... If like this book but feel like you would like to know the details much more in-depth, you can then get Mineral Nutrition of Higher Plants by Horst Marschner, which is a technical text that goes into specifics about the types of nutritients, the concentrations that you can expect under different conditions, their transport into roots and through the plant, metabolism, etc... This book requires a good understanding of chemistry and it is dense, with lots of tables, figures, and data.