Nothing is better than facebook.github.io/react/docs/hello-world.html. Official document is the best way to learn any new technology.

I managed to snag the Udemy course 'Modern React and Redux' when it was on sale recently. The course is presented by Stephen Grider and I found it to be a comprehensive introduction into both the coding and the reasoning behind the way react/redux is coded.

I was impressed with the way that Mr Grider presented that, having completed the course, I enrolled in a number of his other courses.

Udemy seems to have sales periodically, so it's worth checking back now and then if the course you want is currently full price.

Signing up to a newsletter or following popular twitter feeds that share content from ReactJS can be a great way to learn. Reactdom is one such newsletter and twitter account that shares all the best ReactJS stuff.

Just to add to these wonderful comments, it would be very good if you could search for some articles in which the author mentions about the struggles that they faced while learning React for the first time. Learning those things will help you understand the concepts easily.

Also, don't forget to checkout this free course by Tyler McGinnis.

I know it costs a little bit of money but I took both the starter and the advanced course and it really hit it home for me. starter, advanced. If the links do not work just go to Udemy.com type in react and the courses from Stephen Grider. I hope this helps. They sure helped me understand it very well.