Does shotgun messiah vol 7 work for non shutgun users?

[ElCabong]

It's a 20 percent extra damage if the target is at full health. Useful for anybody.

[Boidster]

I don't think it does. I looked in progression.xml which is where the books' effects are described and all of the effects for the books are tagged with 'perkBoomstick'. For the specific book you're talking about, for example:

 

<perk name="perkShotgunMessiahPartyStarter" parent="skillShotguns" max_level="1" base_skill_point_cost="0" desc_key="perkShotgunMessiahPartyStarterDesc" long_desc_key="perkShotgunMessiahPartyStarterLongDesc">
    <effect_group>
        <requirement name="StatComparePercCurrentToMax" target="other" stat="Health" operation="GTE" value="1"/>
            <passive_effect name="EntityDamage" operation="perc_add" level="1" value=".2" tags="perkBoomstick"/>
    </effect_group>
</perk>

 

Likewise, the equivalent perks for handgun are all tagged "9mmGun". It would make sense to me that this is how the game determines when/for which weapons the perks take effect. So they are not generic. The description probably should be updated to be crystal clear on that point.