The first two chapters are incredibly written and set the tone for the whole book.
Coincidentally, the last book I read was Absalom, Absalom (re-read actually) and reading Didion after Faulkner is like jumping out of the hot tub and into the pool - so cool and clear.
But there's a relation too - water - just like Faulkner tells the whole story in the first chapter, Didion gives away much of what happens up front too. Then she doesn't just go back once and tell what led up to it, but like Quentin Compson she keeps going around finding new tangents and angles, struggling with two things - what happened and how to tell what happened.
This book is about a sleazy arms deal in the Reagan years gone wrong and touches on a lot of the diplomatic hi-jinx the US was involved in the cold war years. The State department lingo and style is a perfect vehicle for Didion's shockingly clear, elegant prose.