Its a classic. For those who don't know its one of the original 'if the germans had won the war' stories. A cute twist is that within it someone is writing a book about what would have happened if the allies had won the war, and is widely derided as ridiculous.
NB, this is incidental to the main storyline, not a spoiler.
I first read this because it was referred to by David Mitchell in 'No 9 Dream'. In fact I went on to read Miss Lonelyhearts by Nathaneal West, which was mention in Man in the High Castle, and then Brothers Karamazov that was mentioned in Miss Lonelyhearts. After that the trail went too historic for my taste...I had hoped the journey would be longer.