that was the code in a19, they have different groups and containers now..
but i do remember commenting that line out once, and it was Books, Glorious Books...
Trusting me is always a crapshoot.

Too many damn 7D2D XML files open in Notepad++.
So it's interesting (and consistent with other A20 lootgroup changes) now.
<!-- *** Crackabook_Shelves -->
<lootgroup name="groupCrackabookShelves01">
<item name="resourcePaper" count="1,5" loot_prob_template="high"/>
<item group="booksAllScaled" loot_prob_template="low"/>
</lootgroup>
<lootgroup name="groupCrackabookShelves02">
<item group="booksAllScaled"/>
</lootgroup>
<lootgroup name="groupCrackabookShelves" count="all">
<item group="groupCrackabookShelves01" count="1"/>
<item group="groupCrackabookShelves02" loot_prob_template="veryLow" force_prob="true"/>
</lootgroup>
If I read that correctly (remember - crapshoot!), here's how looting a Crack-A-Book shelf would work out. The count="all" for the parent group means, I think, that each sub-group is always rolled. However, the force_prob on the second sub-group means, I think, that the .05 probability for 'veryLow' is used. That is, normally count="all" would mean at least
some loot from every sub-group would be given. In this case, though, the groupCrackabookShelves02 is forced to keep its .05 (5%) chance.
So it works out to about a 25% chance of finding a book or schematic in a Crackabook shelf (not the bookcases you find in libraries/offices/houses - the store shelves). I used the special vanilla POI 000_loot_new_test (which has like 40x every container in the game in it) to loot 40 shelves and I got 9 books/schematics. So that seems to line up pretty well.
Bookcases are different, and simpler, and more lucrative. Again we have count="all" which I think means every group is checked, but the 2nd and 3rd sub-group also have force_prob="true" so they are forced to use the 'med' and 'low' probabilities.
<!-- *** Bookcase_Loot -->
<lootgroup name="groupBookcase" count="all">
<item name="resourcePaper" count="1,5"/>
<item group="booksAllScaled" loot_prob_template="med" force_prob="true"/>
<item group="booksAllScaled" loot_prob_template="low" force_prob="true"/>
</lootgroup>
Mathing on that a bit results in the chance of at least one book = 60%. I looted 40 bookcases and got 27 books (67.5% - I guess I was lucky), including 4 instances of 2 books found in one bookcase (exactly the 10% expected occurrence of that).
Setting aside all the math and the crapshoot on my reliability - just looting all the Crack-A-Book shelves vs. bookcases in the 000_loot_new_test POI showed me that if I want to find books/schematics, I should prioritize bookcases in homes & offices, not necessarily Crack-A-Book stores. The stores have the benefit of a dense group of lootables, but the bookcases are more lucrative.
It seems like the loot tables have been spread out over a larger range of loot/gamestages and that completely changes progression for a solo player like myself. More gates only serve to shut people out.
In a different thread, schwanz9000 acknowledged the wobblyness of the current loot probabilities and is working on a balancing/fixing pass through them. There are leftovers from previous releases which are kind mucking things up. Alpha software, amirite?