Thinking, Fast and Slow by Daniel Kahneman is a copyrighted work, which means official "free" downloads are typically limited to rather than open-access PDF sites. You can access it for free through the following legitimate channels: Legal Ways to Access for Free
Most public libraries offer the ebook and audiobook for free to members via the Libby app or OverDrive . Thinking, Fast and Slow free ebook download
You can "borrow" a digital copy for a limited time through the Internet Archive's Open Library. Thinking, Fast and Slow by Daniel Kahneman is
Some library systems provide instant access to the ebook via Hoopla Digital . Thinking, Fast and Slow free ebook download