How to use an I2C chip? (Adafruit MMA8451)

I've noticed something.
Other implementations of read take a registry variable, and then write to that registry first and then read the first byte from the device, but after a lot of testing it seems that the first byte here is always either 0 or 255
The device sets that byte from 0 to 255 when this is called:

    // Activate at max rate, low noise mode
    this.writeRegister8(this.MMA8451_REG_CTRL_REG1, 0x01 | 0x04);

After work I'll go back and look at the datasheet, but I am wondering if perhaps it just always sends the data in the array back in the same order, no matter what is sent to it.