N1 will not give you anything, but N1 Revolutions per Minute..
EPR will give you the amount of air, passing trough the engine, thus showing you, how powerful the flow of air is.
let me bring in an example- you start your car on the ice-
you push your accelerator pedal, but.. you stand on the same place!
you look at the tachometer and you see, that your engine works, but you do not have any speed. so in that case Tachometer will be your N1 and speedometer will be your EPR. and, in order to read information correctly, I'd read speedometer...
and in every manual you will see, that the thrust of a jet engine should be measured with the help of EPR gauge, not N1.