Normally any book from O'Reilly is great for focusing practical information to get you up and running. Not so with Oracle Essentialls. This book provides an overview of Oracle theory, with very little detail for actual usage.
Example: Tools for Creating Databases. The book mentions you can use the java GUI or the "character-mode scripts". Unfortunately, no advice is given on where to locate the GUI or the character-mode scripts. Further, no examples of running the scripts exist at all - not even the name!
In all, I found this a disappointing offering. If you're looking for a broad overview of Oracle this might be a useful book. If you actually need to bring an Oracle system up and running, this won't be much help.