The Man in the High Castle, Philip K. Dick
The idea is inspired, but not the execution.
You can tell it's written by a pro, a good writer. The imagination is subtle: you feel it is boundless, due to the little bits of fantasy you get in all domains, from jewelery to politics to language to food.
And yet it is moderate—what's the word for "correct dosage?:" that's how the imagination is used.
Unfortunately, the characters are dull, and the story is dull. Like Dick had this great idea but sat on it too long and forgot how he wanted to go about it, but did it anyway.