I like this book as an intro, and although it discusses Java, it does not assume prior Java knowledge and does pretty good walk-throughs of things involving Eclipse.
If you're going to be a serious Drools coder you'll likely pickup another book with more in-depth java. But even experienced developers may appreciate the walk-throughs of Drools lingo, concept and UI that are not obvious, or perhaps not what you'd expect.
The author does a very patient walk through of various procedures for those using Windows and who might not normally work from the command line.
A few warnings: (and not really blaming the author for these)
* You'll notice odd words like "noJPGy". I think this was caused by a global search and replace that somebody did to change graphic file extension names from *.tif to *.JPG, but didn't limit it to "whole words only". So the word "notify" is changed to "noJPGy"
* In the pom.xml files, if you get errors, change the version numbers where it says something like "[5.0...)" to just "5.5.0.Final"
* If you're on Unix / Mac and understand Maven, you might remove the local repository override, so that it defaults back to ~/.m2/ I think the override was done for Windows users.
* The Guvnor UI has changed since this book was written. For example, in the left nav bar, "Rules" is now called "Browse". In some cases where it says to click an icon, you'll need to instead mouse over text elements and notice that become underlined - indicating that you click the word instead of an icon.
* The Jar file names have changed.
* If you're using Java 7, you may get errors about the version of the compiler. Update your Drools runtime to 5.5 and you'll be OK. (this is a frequent problem with open source libraries for those going from Java 6 to Java 7) In Eclipse, one file that had this error was (oddly) the Excel .xls file.
So although the book could use an update, this author is very patient and this is probably the most gentle intro to Drools and Guvnor that you'll find.