Michael Nielsen, co-author of the de-facto standard textbook for quantum computing [1], has an accessible "Quantum Computing for the Determined" video series on youtube [2].
(There used to be a pdf of the textbook online at [3], but it seems to have been removed...)
Scott Aaronson's Quantum Computing Since Democritus [4] is also good, but at a more abstract level. The well-written lecture notes it's based on are on his site [5].
General quantum physics knowledge can also help, but physics-focused content tends to focus more on the calculus whereas quantum computing mostly only uses the linear algebra. I liked The Theoretical Minimum [6].
