tl;dr: Knuth's landing page for The Art of Computer Programming catalogs the current status of all volumes: Volumes 1-3 (fully published), Volume 4A (2011), Volume 4B (2023), Fascicle 7 of forthcoming Volume 4C (2025, on constraint satisfaction), and Volume 5 (Syntactic Algorithms) still in preparation. The page warns readers to only buy the PDF eBook editions since non-PDF versions (Kindle, ePUB) mangle the mathematics, and it links to extensive errata files plus the famous $2.56 hexadecimal reward for finding errors.