So I saw The Day After Ragnarok way back when it was being offered for the up-and-coming 6th edition of Hero system. At the time, my group was using 5th ed. Hero for all our games and I was intrigued by the idea. But alas, I had decided not to jump on the 6th edition train, giving that I had invested so much into the earlier version and it worked perfectly fine for any genre we wanted to play in.
Skip ahead a year or so, and I had grown out of trying to use Hero Designer to make every vehicle, NPC, weapon, and so on. I began searching for a less crunchy rules system that fit my GMing style of coming up with stuff on the fly during gaming. I picked up several books using the Fate system, including the excellent Fate Core and Strands of Fate, and was amazed at the flexibility and levels of simplicity in the system. Now that I've played several games (both running and playing) in various genres, I can say that it is the system I was waiting for.
Now, once again I see The Day After Ragnarok, this time offered for FATE and may I say, it is as interesting and engrossing a setting as I imagined. Post apocalyptic has always been one of my favorite genres to play in, and combined with the technology and history of a post-WW II world, and you get a very unique setting. I would say that if you are using FATE now, then pick up this book if for nothing else then the various creature descriptions and the entertaining sidebars. If you are looking for a post-apoc setting with something a little different then your run of the mill, then this fits the bill. And if FATE isn't your cup of tea, TDAR is still offered for Savage Worlds and Hero 6th ed.