What are some highly specialized fields that require reading books instead of Google?

I am working on an academic project where I am supposed to train an AI model on a niche technical or theoretical knowledge which isn't fully available or easily accessible on the internet. The niche-oriented data must be something that requires heavy research or can be only obtained by reading books and papers etc. My aim is to train the model using Books, Articles, Research Papers etc. So that the model can excel in the niche domain. Please don't hesitate to drop every single thing that comes to your mind which might be suitable for my project. Thank you!