Fundamentals of Soil Ecology by David Coleman et al. (2018) is a very readable introduction, and attends to not just the microscopic, but macroscopic soil food web, too. It is small enough to take out for a walk with you, or on public transport.
A whole book on nematodes, a useful reference. It could become a fascinating world of dicovery, if one wanted to dedicate totally to this field.
It has some good drawings (better than photos) on morphology, but the older prints (like mine) could have better quality images, so might be worth checking out the most recent one.
Described are applications to different cropping situations – vegetables, cereals, oil seed, orchards among them.
The main info is on nematodes to control pest invertebrates, such as insects pest, slugs & snails. There are 2 slim yet worthwhile chapters on the role of predatory nematodes for the control of root feeding nematodes and fungal-feeding nematodes for control of plant pathogens.