If you are going to be using Internet protocols, doing network programming, or web programming with Python, and these are new topics for you, I would highly recommend this book.
The book starts with a brief overview of the Python language. The author's intention is that someone with a fairly extensive programming background in other languages would be able to pick up enough Python from this overview to be able to do the rest of the programming in the book. Perhaps so. I already know Python, but did find the summary in the front informative.
I really like the fact that nearly every page has a code snippet on it. Examples are brief and to the point. The author explains each line of code and has a very direct and clear way of explaining things. I found the explanations easy to read and understand.
After the brief Python Language overview, comes an overview of sockets and socket programming. I've been trying to learn a bit about the whole topic of sockets by searching the web and nothing I found on the web explained it as clearly as this book. I now appreciate the difference between TCP and UDP protocols and have an idea of the situations in which I would want to use each. If you want to learn low-level sockets, or how to write your own socket protocols, this is not the book you are looking for. This book basically assumes you will go with either TCP or UDP (and ignores the other types of sockets available in the Python socket library). However, these will probably suit most people's needs.
The author then walks you through each of the Internet data-handling libraries in Python, such as the telnetlib, ftplib, poplib, smtplib and so on. He gives examples of working code for each library, showing first how to implement clients, and later on how to implement servers. If you want to work with these libraries, these explanations should be very helpful.
Later in the book, Holden addresses using databases in Internet programming, using XML and writing your own web-application framework. I haven't yet had a chance to go through these chapters in detail (I've skimmed them only). But there is a LOT of stuff there. One thing the author does at the beginning of each new section, is give an overview of the topic (such as an overview of why you might want to use a database, how databases work, or why you might want to work with a web framework). For me, I really appreciate this type of overview. It helps give me a context for the new information, and helps me to make better sense of it. I read through some of the database chapters where he explains how the SQL query language works, and again, I have to say it is one of the best explanations I've read. (Most explanations I've read about SQL have just convinced me I wanted to steer clear of it.)
Another nice thing, is how he sort of "works you up to" SQL. He starts out with regular Python code, and shows how parts of it are similar to working with an SQL database, and then eventually transitions into the full SQL language. He also addresses database design and efficiency.
Overall, I'd say if you want a good overview of the topics mentioned here, want to understand the reasoning behind their use, and want to be able to understand good design and efficiency, then this book should really help you out.