Hi, I'm Kim Haase, one of the "et al" authors of the Tutorial.
Your guess is a good one. Volume 1 focuses on platform basics and on web and web services technologies, which are fundamental to the platform, since most
Java EE applications nowadays are web applications. These include JavaServer Faces (
JSF),
Servlets, Contexts and Dependency Injection for Java EE (CDI), and Java API for RESTful Web Services (JAX-RS).
However, if you are already familiar with web technologies, Volume 2 covers important technologies such as Enterprise JavaBeans (
EJB), the Java Persistence API, the Java Message Service (JMS), and security, which are necessary for a full understanding of the Java EE platform.
Technologies new to the Java EE 7 platform are distributed between the volumes: Java API for WebSocket and JSON Processing are in Volume 1, while Batch Processing and Concurrency Utilities are in Volume 2.