What's scary is comparing the old versions of the Edmonds Cook Book with the more recent versions and seeing how much more sugar we're putting in a lot of the stuff we're making.

Would be fun make the same recipes from different editions and compare. I've noticed some minor variations between my parent's copy and mine but neither are really old.

I remember my ANZAC biscuits recipe in particular has less butter and more sugar, like you say, and is clearly inferior. A bit sad. However we also have Edmonds: Best of Baking, which is newer than my Edmonds Cookbook, and prescribes more like the old recipe with more butter.

I remember looking up eggnog recipes and realizing that the 1950s used twice as much whiskey as the modern versions

That was some good eggnog

Looking at recipes on the Internet it seems eggnog barely contains any whiskey by volume. By comparison German Eierlikör consists mostly of korn (a 32% ABV clear liquor similar to vodka) or white rum.

I'm not sure what 1950s eggnog looked like but I'm guessing it was more like the German style Eierlikör (i.e. made mostly with liquor and eggs) than the modern eggnog (i.e. mostly milk and cream).

Was the whiskey of the 1950s lower proof?

Definitely not. In fact, I think more of it was probably bonded (100 proof).

We recently had a 2nd hand copy shipped to NYC to bring a little bit of home back to the kitchen.

It’s almost like the Michelin: intended to sell more of a product (tires/flour), but ended up iconic in its own right.

Some of the more basic “the Good Housekeeping Cookbook” earlier editions (50s, 60s) are nice and basic; aren’t flashy, but you get the basics. Rabbit Stew, Gumbo, and 1000 others.

Do all the "cooking bibles" assume a specific cuisine?

Depends on the book. For example, Joy of Cooking is pretty standard American and Italian/French-by-way-of-America fare (unsurprisingly, since it was first published in the US in 1931), while How To Cook Everything has a much wider remit.

Yes, in my expericen they all kind of do.

This doesn't mean that you won't find recipes from a foreigen cuisine in them. Most of them are however adapted to the cuisine the book is from.

Sometimes it's a recipe that is basically unknown in it's country of supposed origin (Spaghetti with meatballs).

But often they are only adapted to the different preference in taste, or the different things you will get at the grocery store.