I'm not sure you ask about the book creation, the platform update or the performance factors you want to consider on a EE 8 app so I'll try to give some points for each of these options and let you
ask more questions on the particular one you are interested in.
Book creation: the main rational was to try to give the needed entry points and keys for anyone to work on performances on any JavaEE 8 application efficiently and autonomously. It was not about giving particular solutions which rarely work in all cases but more the way to understand any case and work on them.
JavaEE 8 update: main new features are about the language evolution and the modern programming models. This means more reactivity (CompletionStage etc), and java 8 types (dates, ...) support in specifications. There are also some new specification like JSON-B (java-json mapping).
Optimization factors in JavaEE 8 applications: avoid locks on the main codepath and rely on the platform when possible for the locking and thread safety, reactivity when possible (websocket, CDI async events, JAX-RS AsyncResponse, ...), tunning as usual (GC, connection pools, instance pools, ...), caching where possible.