I dont understand this page in my book. According to it , if voltage values at drain and source are inverted(to the gate input as shown in case 1), it has highest capacitance. how exactly is gate capacitance data dependent?
In the inverting configuration the Cgd component 'looks like' a larger capacitor connected to ground because you must supply charge to change the voltage across Cgd from +Vin to -Vdd, rather than just fron +Vin to 0.
So it might effectively double that component of the capacitance if the swings are the same. The same thing applies to other capacitances and other terminals of the device. See Miller Effect.