We (Brilliant) do have an introductory course on quantum mechanics as well. It goes into more of the phenomena (like spin, photons, etc.) than this computing course that mostly focuses on information. Let us know what you think: https://brilliant.org/courses/quantum-objects/

If Brilliant isn't your cup of tea – check out mcintyre's spin-first treatment. Generally speaking avoid any textbooks with cats on the cover (ie. Griffith's is popular but only so-so IMO). That being said, we went with a cat on our course ¯\_(ツ)_/¯.