The inclusion of Anathem and A Canticle for Leibowitz in a library intended to survive through a societal collapse does seem appropriate.
I usually avoid Stephenson (only because it's so wordy and I don't have much free time) and hadn't even read the wikipedia tl;dr of Anathem, but you mentioning it together with A Canticle for Leibowitz caused me to read the first few paragraphs of the wiki page for it and now I'm going to make an exception and find time to read it.
Thanks!
On the topic of "bleak" and "societal collapse", it is notable that they chose "Blood Meridian" over "The Road" in Cormac McCarthy's works.
Blood Meridian is an account of how we got here. If civilization falls apart to the extent that they need this resource, they'll at least presumably know how they got there and won't need a fictionalized account of societal collapse.
Blood Meridian is generally more highly regarded, no? Wiki states it's widely regarded as his magnum opus and a "Great American Novel".
I'm now reading _East of Eden_ for the first time.
If it's about "who we were and how we got here" I'm surprised that that there's no Steinbeck.