I tend to read a section carefully, then close the book and try to reproduce the example without looking at it again. Of course I'll allow myself to use online reference material, as I do in real-life programming. If I really get stuck I'll take a look at the book, but just enough to unstuck me. The goal is obviously not to reproduce the example line by line but to reproduce what it does with the same global structure.

I've found that it's easy to zone out if I'm just typing exactly what's on the page in front of me. Following along but in a different language can keep you more engaged and think more about what's going on.

It also becomes a bit of a battle against the desire of copying/pasting the code (It's even more tempting since it's an e-book with the code already formatted), not to mention that some parts are tedious to type like enumerators with many string elements

That's a good point. I also have a problem with zoning out when reading technical books. I should give your technique a try.

I unconsciously change variable names when typing code samples which later forces me to track data flow and dependencies