Daal, I know reading is something very basic, but I don't see it as a "principle". Reading is endless, and it does not give any information to me if someone says "improve your reading and you will be dan player in no time".
If someone talks about some basic principles, there must be a well defined set of rules to study. Otherwise it is equivalent of saying "play only good moves and you will be very strong soon". It is true but does not contain any useful information (it's entropy is nearly zero
)