If you ask a hardcore Doctor Strange fan what’s the main comic book story to read starring the good Doctor, chances are they’ll mention The Oath first.
However, while the cinematic Nicodemus has simply been described as a “rival scientist,” his comic book counterpart actually wielded mystical forces against the Sorcerer Supreme.
As far as self-contained tales go, outside of Strange’s origin, The Oath definitely should rank at the top of your must-read list.
The Oath also followed Strange trying to heal Wong from his terminal cancer.