You may not have realized this, but since the beginning of this book we've been working with the new DotNetNuke menu, commonly referred to as the DNNMenu. From version 2 of DotNetNuke, the menu called SolPartMenu has been the default. The new menu has been designed to be more efficient and flexible.
Here are some quotes from the core team member Jon Henning, the author of both the old SolPartMenu and the new DNNMenu:
The SolPartMenu is old and carries a lot of baggage with its almost worth 4 years of backwards compatibility. It has been a goal for v2 of the SolPartMenu to abstract all of the common logic not specific to the menu into separate JS files that could be reused by other controls and applications. This is exactly what the ClientAPI is—an abstraction of logic like positioning, DOM access, XML, etc. The script for the menu should contain only the code for the menu, thus making it easier to maintain and enhance. So in essence, the DNNMenu is in a lot of ways the SolPartMenu...