I have many electronic versions of Feng Shui, Four Pillars, Qi Men, and Zhouyi, but it is too troublesome to upload them to the Internet!
Li Juming's "The First Book on Learning Feng Shui" can be read as an introduction, but it is a bit simple.
The Zhongzhou School Xuankong Feng Shui information can be searched in Baidu Wenku, and Sina Wenku is also available.