But wouldn't just really-really reading it do the same thing more efficiently.
I've learned tons from using Firebug. In part because I could start with prewritten code and tweak, and read, and tweak, and read. If I had to enter all the code manually into Firebug (no copy and paste), I think I'd have better muscle memory for typing some of the stuff, but I don't think I'd be a better developer for it (not that I'm a web dev, but just sayin).
Most people's brains aren't trained for reading things properly unless it's with the intent of immediately applying what they read. They can try really hard to read carefully, but their brains are simply not in the right mode to absorb the material the same way they would if it were being put to use. It's hard to even become consciously aware of how poorly you're learning, because it feels like you're really concentrating.
I've finally gotten to the point where I can tell when my brain isn't learning like it should, but I still can't just will that mental state away.
"But wouldn't just really-really reading it do the same thing more efficiently."
If it works for you, go nuts. It's a surprisingly rare skill, but I think it exists. Every once in a while I can reach that level (mostly in code reviews; for some reason that makes it easier).
I've learned tons from using Firebug. In part because I could start with prewritten code and tweak, and read, and tweak, and read. If I had to enter all the code manually into Firebug (no copy and paste), I think I'd have better muscle memory for typing some of the stuff, but I don't think I'd be a better developer for it (not that I'm a web dev, but just sayin).