I don't see anything about one of these books being an actual, out-of-the-box campaign. Is that a typo or am I missing something?
It's not really a typo more that it is not 100% clear in the wording. Both books are not campaigns in they are essentially a players guide and a GMs guide. There is however tons of campaign backstory, hooks and world detail in both.
There are two linked adventures already published in the series however, and they have named this campaign Achtung Cthulhu. I suspect this is what the last few lines is actually referring to. (Three Kings starts in 1939 for example)