This is a coder's book. It's intended to help developers build applications that make use of T-SQL. It's not about database administration or design. It's not about end-user or GUI application development. It's not even about server or database performance tuning. It's about developing the best T-SQL code possible, regardless of the application.
You'll have to judge for yourself whether these goals have been met, but my hope is that, regardless of the degree of success, the effort will at least be evident.
This book uses SQL Server's Northwind and pubs sample databases extensively. You'll nearly always be able to determine which database a particular example uses from the surrounding commentary or from the code itself. The pubs database is used more often than Northwind, so, when it's not otherwise specified or when in doubt, use pubs.