I never got fully through it, but Amelia Wattenberger's book [0] on it is very good! There's a fairly soft ramp up in complexity, and the later chapters are complex enough that even the previews make you excited to reach and implement them.
If you just want to dip your toes in though, the official website's linked gallery [1] is a pretty cool resource. No set up or data loading required!
D3 is very powerful, but there's a lot to learn too!