Yes, I found it weird that the book is not on this list, but clearly the author is geared towards python - although web development might be the only area where Ruby outshines Python.
We'll be sure to check out the book for the Ruby version of the Path.
That said, this is just one web-dev path and doesn't in any way claim that Python is superior to the alternatives. There can be so many more - on RoR, Node or even more recent ones like scala .. hope experts will help us build those. If you are interested, please write to us at contact@mysliderule.com!