Few authors can make your brain cramp like Heinlein. By His Bootstraps is a masterclass in the closed time loop. The story follows Bob Wilson, a grad student who gets pulled through a time portal—only to discover that he is the one who creates the portal, gives himself the idea, and ultimately tricks himself.
PDF (Public Domain) Rating: ⭐⭐⭐⭐ (4/5) by his bootstraps heinlein pdf
Since the copyright wasn't properly renewed in the US, you can legally find the PDF on sites like Project Gutenberg , Internet Archive , or ManyBooks.net . ⚠️ Important Legal Note for you: While By His Bootstraps (1941) is often considered public domain in the U.S. due to a failure to renew copyright at the 28-year mark, always download from reputable sources like Project Gutenberg or The Internet Archive (archive.org) to avoid malware. Do not post direct download links to copyrighted scans if you are unsure of your local laws. Few authors can make your brain cramp like Heinlein