The business rules approach offers a solid advancement in systems development and Barbara's book expounds concrete steps that you may take to implement the method in your organization.
My principle criticism of the text is that the first half of the book has been poorly edited and is almost impossible to read. There are many sloppy sentences, grammar errors and redundant constructions. Because this topic is important to me I took several weeks slogging through the book to adsorb the materials I needed. This should have taken much less time.
The book takes a very strong relational database approach to the mapping of terms constraints and facts. If fact, a substantial portion of the book is devoted to recycled relational data modeling and for some reason this part of the book is more flowing and eloquent. The text's arguments are weakest when the author presents a poor understanding of current object technology. For instance, there is no discussion of patterns and many of the declarations of the limitation of Object Technology are uninformed. I would suggest that those with OOSE orientation overlook this bias. There is some good material for OO practitioners.
There are two competing views in the business rules camps. One view is that business rules presents and solid requirements gathering technique. The next view is that business rules are all about application generation. The first technique has spawned software product that 'listen' to the data in the database in a 'rules engine'. Barbara Van Halle describes these tools. Eloquent presents the second view.
In summary, if you are seriously considering the addition of business rules methods to your project or organization then buy and read this book otherwise wait for a second edition.