A 'flock novel' could potentially refer to a novel that has something to do with a flock. For example, it might be a story centered around a flock of birds, or a group of people or animals that behave in a 'flock - like' way, such as a flock of sheep. However, without more context, it's hard to say for sure.
I'm not entirely sure what a 'flock novel' specifically is. It might be a very new or niche concept, or perhaps it's a term used in a particular community or by a certain author that I'm not familiar with.