Playbooks

Read Option out of Pistol Strong 21 personnel is a designed run play built around the zone read mesh point between the QB and the HB lined up behind and to the side of the QB. The offensive line executes a zone blocking scheme, sealing the point of attack while the QB reads the backside end man on the line to decide whether to hand off on the inside track or pull and attack the edge. This is a pure run play with no route concept attached, so the primary read progression is the QB's mesh point decision on the defensive end, then the HB's aiming point based on the blocking flow up front.
Watch the defensive end assigned to the read side. If he squeezes down to take away the dive, the offense will pull and keep with the QB, so a disciplined edge defender who stays home neutralizes this play. Stacked linebackers who fill downhill fast can blow up the interior zone lanes before the HB gets to the mesh point, so playing linebackers tight to the line is a strong counter. User the play side defensive end and force him to widen or crash inconsistently, since a jumpy CPU or user rush read makes the QB's decision easier and opens the alley. Overloading the box with an extra defender (nano blitz look or a safety creeping down) can outnumber the zone blocking scheme and force a negative play if the offense does not have a lead blocker to account for the extra man. Contain-based defensive fronts that keep the QB boxed in the pocket area take away the edge keep option, forcing the ball inside where stacked linebackers can rally and make the tackle.
Use this play on early downs (1st and 2nd and short to medium) when you want to stay ahead of the chains and keep defensive coordinators honest against your pass calls out of the same Pistol Strong look.
Check the defensive end's alignment before the snap. If he is crashing hard down the line on tape, key on pulling the ball and attacking the edge with the QB. If he sits wide, hand it off and let the HB work through the zone blocking lanes.
Combine this with HB Power, HB Off Tackle, and HB Counter from the same formation to keep the defense guessing between zone and gap schemes without changing your pre-snap alignment or tipping your play call.
Watch linebacker depth pre-snap. Stacked, tight linebackers are keying run and will crash downhill, so consider pulling the ball on the QB keep to exploit the alley the defensive end vacates.
Avoid calling this against heavy blitz packages up the middle unless you have confidence in your zone blocking to hold up, since the mesh point takes an extra beat and can get blown up by an unblocked interior rusher.