This is the second book set in VanderMeer's wonderful city of Ambergris. I just adored City of Saints and Madmen. While I think you could dive right into this book and still enjoy it, I would recommend you start with City which not only sets the stage for Ambergris but includes many of the same characters and events relevant to Shriek. Unlike City, which is a collection of short stories, letters, pamphlets and scholarly articles, Shriek is written in a more typical novel format. The book supposedly is a manuscript written by Janice Shriek, a former art dealer, about the life of her brother Duncan Shriek, a former historian. It includes editorial comments by her brother inserted in the text in brackets. But it is more than a story of the rise and fall of these two fascinating siblings. Through the story of the Shrieks it gives a detailed picture of an entire generation of the inhabitants of the city of Ambergris, from its cultural and academic life, to its descent into war, to its mysterious underground populated with the gray caps and their fascinating fungus. Ambergris is richly imagined and VanderMeer's wonderful prose makes it unforgettable. Although a dark mysterious and dangerous city, Ambergris is one of the most intriguing imaginary locals I have ever encountered.
The story of Ambergris is continued in VanderMeer's new book, Finch, which has been nominated for a Nebula award. Although I bought it as soon as it came out , I think I will hold of reading it for a while so I can savor Shriek. My understanding is that it is a novel cast as a noir detective story which takes place a century ofter Shriek when the grey caps have come to power. It has gotten good reviews : here is one from Carl V.
I read this for Once Upon A Time, Mind Voyages and Speculative Fiction Challenge.