I'd recommend 'Parasyte' for its intense and disturbing storyline. It combines horror with sci-fi elements really well. Another good one is 'Tomie' by the same author as 'Uzumaki', known for its psychological horror.
A horror manga is a must-read when it has a fresh take on the genre, maybe by combining horror with other elements like mystery or fantasy. Good world-building and a consistent tone throughout also contribute to making it a must-read.
The main difference is usually in the visual style. Anime horror manga often has a more dynamic and exaggerated art style compared to regular horror manga.
One must - read horror story is 'The Shining' by Stephen King. It takes place in an isolated hotel with a family as the main characters. The father slowly descends into madness, and the hotel itself seems to have a malevolent life of its own. Another is 'Dracula' by Bram Stoker. It introduced the world to the iconic vampire, Count Dracula, with its dark and gothic atmosphere, and the battle between good and the undead. 'The Exorcist' is also a classic. The story of a young girl possessed by a demon is truly terrifying and has been a benchmark for possession - themed horror.