Because they're so complicated, many books on relational databases are either burdensomely academic (Database Management Systems is the classic example of this mode — it's superb, but one practically needs a professor to help you decode it) or so practical-minded as to be overly simple. Designing Relational Database Systems has struck an attractive balance between the two extremes by providing enough theory to enable you to design your databases intelligently, while keeping in mind real-world business practices and the practical limitations of actual database management systems.
Author Rebecca Riordan emphasizes Microsoft database products to a small degree, using Microsoft Access and the Jet engine in some of her examples. The Microsoft overtones aren't overpowering, by any means.