Ask HN: How can I get started with VR/AR?

Hey everyone! I'd love to get into AR/VR development, I understand 3D packages (Houdini/Maya) and programming (webdev) reasonably well, but have never tried doing any gamedev.

What is the best way for me to learn how to develop AR/VR apps? Should I learn Unity or UE? Are there any good books/courses? Any more tips/advice?