The suggested price of Rationality: From AI to Zombies by Eliezer Yudkowsky is $4.99 and is also the price for the Kindle version of the book. However, the book is available on the official website in a 'pay what you want' model, meaning you can download the book for free and eventually pay for it later.
Ranked in these QuestionsQuestion Ranking
Pro Will make you smarter
Your intelligence is being used to defeat itself. Learn how to stop that.
Pro Fictional interludes
These are quality science fiction short stories in their own right.
Pro Mindblowing ideas
From (friendly) AI to (philosophical) zombies. Also Pebblesorters. And why humans are insane.
The chapters are relatively short and digestible essays and short stories. The problem: there are 333 of them. On paper, this would take volumes, but this is an ebook. You'll get a lot out of it long before you finish though.
Con Has some highly technical references in places
Things like physics (relativity, quantum mechanics), mathematics and computer programming. Scared? Didn't think so.
Con Not enough citations
Just Google it.