Lately I'm starting to think that most important part of Feng Shui is understanding how Qi moves and how it gathers.
While we can go deeper into that with Qi Gong, there are some texts that help with understanding it from another angle.
One of those for me is the Water Dragon Classic. With preface from Dahong(was first time I read something from him and he does seem like a very important path in these systems) it gives the interesting idea of how to work with forms on flat river land.
Dahong is the source from where XKFX from Shen(Flying Star) and XKDG are based on.
That translation... It was originally included in the 5 feng shui classics books, here is link to chapter 3(coz I love chapter 3) from interesting website with info:http://www.davidyek.com/yifengshui/-water-dragon-classics-3