You can't legally set V2=Vr because of
Originally Posted by FAR
§25.107 (c) V2, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by §25.121(b) but may not be less than—
(1) V2MIN;
(2) VR plus the speed increment attained (in accordance with §25.111(c)(2)) before reaching a height of 35 feet above the takeoff surface; and
(3) A speed that provides the maneuvering capability specified in §25.143(h).
Item (2) means you have to account for the "speed spread" between Vr and V2 - the aircraft physically MUST accelerate between Vr and v2, and that has to be taken into consideration.
But fundamentally JT is correct - the book should cover this, if it doesn't I'd strongly suspect an error - unless you're doing something so unusual you are the first person to encounter this....