Its a python book targeted at people who have just had a rudimentary introduction to the language. It aims provide a deeper understanding of the language for such users.
The experience with Leanpub was quite fantastic apart from the occasional outage for maintenance. The variable pricing is something that I really do like. As for having more books planned, I like to share what I know so I will definitely be writing more books and using Leanpub for that!
Python if looking at a dynamic language! It will get you up and running in no time; the syntax is also very easy to understand and easy on the eyes...If you want a statically typed language then go with Go..it feels like python with types