I like the frame on this one. They are projecting his story outward in case there are alternate universes out there, to warn us. He discusses what he probably has in common with the recipient -- but you should hang on, even if you know how steam boilers work or World War II, because too much information is better than too little.
Then he talks about his part in the push near Oregon. . . yup, you don't know who fought World War II, or where. But our hero, being a werewolf, is pulled in on a special mission; they are sending a witch and her familiar into the enemy camp to deal with an afreet that the opposing forces are about to let loose from its Seal of Solomon. And when he is wounded and unconscious at one point, he has a dream encounter with a powerful and evil being. And dismisses it as a hallucination of some kind while he gets on with it.
The witch, named Ginnie, and he deal with that, end up going to college after the war -- where a prank goes very wrong -- and marrying -- and they have an uncanny encounter on their honeymoon.
It is after this, and the birth of their daughter, however, that they learn that there was indeed a thread tying together these things, and that its consequences are even worse for them than they had realized. They have to face up to a bigger foe than ever before.
A tale involving stained glass windows, a horrendous stench, a ruined castle, a cat named Svartalf, brownies who get revenge for what Svartalf does, flying carpets, two dead geometers, and other wonders.