Reddit reviews The Bunch Attack: Using Compressed Formations in the Passing Game (2nd Ed.)

Concept Passing: Teaching the Modern Passing Game

The Bunch Attack: Using Compressed Formations in the Passing Game

Run-And-Shoot Football: The Now Attack

Lavell: Airing It Out

Bought all these when I wanted to learn more about the passing game.

Oh how do I love thee, let me count the ways...

I could write a whole book on this here but, alas, some guys I know already have (Dan Robinson is a mentor of mine and I have had some correspondence with Andrew Coverdale as the head coach I worked under a year ago spent a few years working with him at Trinity HS in Louisville, KY):
https://www.amazon.com/Bunch-Attack-Compressed-Formations-Passing/dp/1606793365/ref=sr_1_1?ie=UTF8&qid=1506465523&sr=8-1&keywords=The+Bunch+Attack

They are both brilliant coaches and reading said book will serve you greatly.

To piggyback off of what @grizzfan stated, one of the biggest advantages in the passing game is you force cornerbacks into the core of the formation, therein the angles for their zone drops become heavily distorted. This distortion leads to a certain lack of comfort for a lot of these guys and that allows a viced formation to "expand quickly" to the edges of the field in both the passing game and the running game.

Likewise, compressed formations with one receiver set out very wide with a "plus split" is a great way to simplify coverage reads for the QB. I don't watch a lot of NFL ball so perhaps McVay is doing this with Goff and the pieces the Rams have added. At minimum, Harbaugh has done this for a long time, going all the way back to his time at Stanford: http://breakdownsports.blogspot.com/2015/03/inside-playbook-harbaugh-michigan-power-O-pass-spread-option.html

One of the other benefits of bunch or viced alignments (vice meaning compressed on both sides of the formation, e.g. a 2x2 receiver pairing but with both exterior receivers having reduced splits) is how it can reduce the distance needed for a throw to the edge. My second year of coaching (been coaching HS ball for 7 years now), we had a freshman who showed great potential but was probably a buck 25 dripping wet; very little core strength and just could not attack the edge of the field with throws out of more conventional splits. As such, we began to use more bunched alignments in our passing game to quickly deliver the ball to a couple of playmakers we had and it helped us greatly.

The other element of a front-side bunch/vice to one-side is how it can create possibilities for an instant, multiple, backside attack which normal spread sets would not afford you.

Bunch/viced sets can also be a great blitz deterrent. Generically speaking, I think it is best to release 4 to 5 whenever possible but there is something about having the ability to show the ability to protect with 7 to 8 it seems like. I don't know if it's a psychological thing for defensive coordinators but it sure does seem like "something" happens when they see bodies available to answer a blitz or overload to the protection that can serve as a means of determent using formation.

I am a huge fan of trips into the boundary and bunch alignments are a great way to dictate coverage. If you bunch into the boundary, it is very tough for a defense to set a 3-deep coverage to the field. If the single high safety cheats to the solo wide split receiver (usually your best guy), there is a potential numbers overload to the 3-receiver surface. If he cheats to the boundary, there is the obvious issue of a whole lot of grass for one (again, usually very good) receiver to work within; perhaps a team cheats out a backer to rob the quick game throws but that then softens said edge for the run game.

Motioning/shifting to bunch can create a lot of problems for a defense. Typically at the HS and collegiate levels, teams frequently have automatic checks they like to go into against condensed/bunch alignments. When you motion into them though, you potentially create some confusion for them and therein you may gain a gap or some kind of + advantage in the passing game.

Definitely, definitely, definitely pick up the Bunch Attack book though. Nominally, it is about compressed formations but there is so much more to learn from it than just that, therein I think it is a must read for anyone.