I know I wouldn't have fully assimilated even half of this book in school: it certainly provides overview material approachable by those of moderate experience, but it will be most appreciated by those who have actually implemented (or are about to implement) much of what it discusses.
Working on a hot new RAID box? Parts of this book will help. How about a file/record/object system? Yup. In either case, more complete references exist (and you'll need them), but the point is that this book really does cover data management from the disk on up in a useful degree of detail.
On the other hand, if you're implementing a transaction manager, this book is both necessary and likely sufficient. Read it first to get started in the right directions, and revisit specific areas as you code - a casual comment is easy to forget if you read it before you fully appreciate its context. The authors acknowledge that there are neat tricks not covered (because they would obscure the core material) that you'd likely want to incorporate once you're sure you really understand their impact, but all the framework, and much of the detail, is included.
Bottom line: If your interest in data management is truly intense, you need this book - it should remain current for quite some time.