Stop books going to the cloud

Is it beyond the Witt of Apple to answer a simple question, this has been asked before but not answered.

How do we stop books going to the cloud, I have very limited data allowance when out and about, sometimes I need to look at one of my books or one of my spreadsheets, where is it to be found, in the cloud, not where I put it or want it, I have masses of storage on my phone, why can’t they stay there, why does Apple insist it still owns my phone and all that’s on it and just moves it as and when it likes.

tell me (us) how to stop stuff just jumping on to the cloud and leaving our devices.