Some of the highly regarded Hellblazer novels include 'Dangerous Habits'. It delved deep into John Constantine's battle with lung cancer and his complex relationship with magic and the supernatural in that context. Another good one is 'The Family Man' which explores Constantine's family issues and how his past family history affects his present and his dealings with the dark forces.
The number of Hellblazer comics varies over time. As of a certain point, there were around X issues, but this could have changed due to reprints, special editions, and new releases.
Hellblazer is not part of Sandman comics. They have no direct connection. Each series has its own themes, tones, and universe that set them apart from one another.
Yes, it is. The Hellblazer comic series is known for its depth and originality. It explores interesting concepts and has a cult following for a reason.
I'd say 'Haunted' is a must - read. It's a dark and intense story that really gets into Constantine's head. The way it portrays his psychological state while he's facing all these terrifying supernatural threats is really engaging. It's not for the faint of heart, but it's a great Hellblazer novel.