I'm not sure where you picked up the idea that I don't recommend reading code. One of the persistent problems in software development today is that far too few people DO read code.
That said, the myth is that pointing at a huge pile of code and telling new developers "just read it" is effective. I think that's possibly the least effective way to learn a project.
There's no substitute for reading code. I certainly don't intend to give that impression. At some point, new developers absolutely must read the code.
I don't think that's the best, first place to start though. Show them a glossary, an overview, completed story cards, or maybe UML. Explain how the pieces fit together. Then (and only then) let them examine the individual pieces.