Teaming with microbes and Secrets of the soil are 2 of my favorite books regarding the microbiology involved in horticulture. Bacteria and fungi are extremely interesting and complex. When you really start diving into the subject I personally think it really starts opening your mind to a more natural ways of working with plants and nature in general. The rate of growth you can achieve with Aerated compost teas is remarkable to say the least. I believe when I started learning about these functions of plant biology is when I really started becoming a better grower. Just a heads up Secrets of The Soil is a little out there for most people but still has some very interesting information and points of view. Also neither of these books are directly geared toward cannabis but both have principles that apply to all plants.