It's a great book (as is this entire series, and I'm not saying that just 'cause I found a typo and point of improvement in Digital Typography_ and got a Reward Check), but one can get the gist of it from:

http://literateprogramming.com/

and finding a suitable tool for your language of choice and doing a small project --- tangle/weave is such a basic concept that it's notorious for folks rolling their own --- heck, I was able to do it (w/ a bit of help: https://tex.stackexchange.com/questions/722886/how-to-write-... )

That said, I bought a second copy as a gift from Thriftbooks.com and it was a reasonable price.