One of the first courses I took in seminary long ago was one on John Calvin. It was a deep dive into theology for someone like myself who was theologically illiterate. I was raised a dispensationalist and didn't know there was anything else. My theology was accumulated through years of drifting mentally and spiritually through sermons and Sunday School lessons. I knew I was a sinner, God hated sin but loved sinners if we repented and wouldn't send us to hell if we confessed Jesus as our Savior who died for our sins on the cross. That was my theology. Calvin's Institutes was my introduction into a real Theology. I have read Calvin off and on ever since. His commentaries on every book of the Bible except Revelation still compare favorably to the best modern ones. Most theologians of note still have to deal with Calvin. That is remarkable considering Calvin had little formal theological training. What he knew he studied on his own and study he did sometimes 23 hours a day. He loved the early church fathers and knew them by heart. He loved the Scriptures except for 2 Peter and Jude and he had questions about James. The rest he knew by heart, too.
His life is fascinating. He married late and adored his wife. He lost many of his jobs over theology and his lack of flexibility. His people skills were notably lacking. Yet, he had an opportunity to try to prove his theology in a real world setting. For a while Geneva was his city. He tried to make it a Christian city and that project did not work out so well. He had few friends but many followers who were not always true to his theology.
Calvin lived nearly 500 years ago. It was a world apart from ours. No tweets, texts, or transportation. What he did have was a theology that has stood the test of time.
A good place to start with Calvin is John Calvin by Herman Selderhuis. Then try reading his commentary on the Psalms and chew on the Institutes from time to time.