If you're looking for something that is a more "immediate" aftermath of an apocalyptic event, that is a tough one to find in fantasy fiction. There are plenty of them in sf and in mainstream fiction, but I think that's because those genres are ones that we can see more as mirroring our own condition, and the role of the post-apocalyptic novel is more aimed at that than anything else. So we have novels like Canticle for Leibowitz (though to say that's "immediate" aftermath is a stretch, I suppose) that looks at it with an sf approach, or more mainstream novels like Alas, Babylon or Earth Abides or On the Beach. But those are all making commentary about Cold War issues more than anything. A fantasy novel just doesn't work that way for the most part. The post-apocalyptic theme of the cautionary tale, or the survival tale just doesn't resonate in a world that we can't somehow relate to our own.
But I would argue that a great deal of fantasy is actually some form of post-apocalyptic tale, though it's more of a "long game" and not an "immediately after" sort of story. Tolkien is a prime example. There was a much higher civilization in the past that has fallen due to war. The story of the LOTR is one that plays out in the ruins of that civilization (often literally). That's just one example. Donaldson's Covenant series, Williams' Osten Ard series, Brooks' Shannara series, Wolfe's New Sun series, Vance's Dying Earth, Jordan, Martin, etc., etc., all take that approach where there had been a prior civilization that was greater in some way (whether it be technologically or magically or culturally). In each case that earlier civilization is gone and the story we read takes place in a world that has risen out of the ruin of the old one.