This is an extremely retro review. I bought this book in my undergrad days, to go with the databases course. I didn't read it at the time, and indeed tried it a little later and found it hard going (or at least tedious). Having actually had to write a few queries now, I've finally read this book properly.
My first surprise is how noddy it really is. It's definitely a first course. While it's got the academic style, with its exercises and its TeX-based layout, the content wouldn't be massively out-of-place in a "SQL for Dummies in 24 Hours" book. It's fundamentally a vendor-agnostic introduction to SQL, with a token smattering of theory, DB design and ODL/OQL thrown in. It certainly doesn't cover DB implementation - data structures, query optimisation, transaction implementation, or any of the cool stuff. The theory gets very sketchy when it gets non-trivial. It's as if the book runs at constant material progress, rather than constant difficulty, so that normal forms are almost skipped while simple SQL constructs are explained in tedious detail.
So, when it comes down to it, I'm not sure who this book is for. It feels like an O.U. presenter at a disco. If it had the intention of gaining serious academic merit, it could have done well, but this is a dumbed-down book, and as such probably does a lot worse at its job than the brazenly idiot's-guide tomes, which might at least give real-world hints and tips.