This perk reduces an enemy's chance to critically hit the player character by 50%. When the Lone Wanderer receives this perk in-game, they also receive a 30% discount at Craterside Supply, and Moira's Repair skill raises to 72% condition (from 54%). This perk does not in itself grant these bonuses (her dialogue checks the quest stage of the Wasteland Survival Guide instead of the presence of this perk).
To obtain this perk, the Lone Wanderer has to talk Moira Brown out of writing the Wasteland Survival Guide. This will negatively impact Karma, and prevent the Lone Wanderer from earning the Survival Expert perk, but will not forfeit the achievement on consoles.
The quest must have been started to obtain this perk. After that, Moira should be asked about the guide and how the Lone Wanderer fits into it. They have to ask her about the research and tell her she does not know what she is doing. After that a Speech check must be passed to complete this. Alternatively, reaching Chapter 3 will offer a speech check-free option to tell her that she will be a laughingstock if she continues, then ask her to stop before she gets people hurt which also results in the same outcome. As such, the Lone Wanderer can do all but one of the final third chapter to receive xp and rewards, then convince her to not finish the book for the Dream Crusher perk.
Many weapons released in Point Lookout have high critical multipliers, meaning this perk comes in handy when traveling into the swamps.