Ask HN: How can I learn about Spectroscopy?

I'm a full stack / machine learning developer. I was reading a few research papers about the use of ML models to diagnose diseases using spectral data. This has made me interested in learning more about how spectroscopy works.

My background is mostly CS and I'm not too familiar with chemistry, how can I start learning Spectroscopy? Please let me know if you know of any courses, textbooks or anything else that can help me learn.