It's ~old book (1988), but it still very actual now, and will be actual in future. This book contain only principles and algorithms, but it all showed so deep and clear, so I was very impressed then read it first time. B-tree type structures description is best I ever seen. (Need to have this book if You perform serious low-level work on NTFS, BFS or other File System, based on B-trees.). And even if You not work with such File Systems - this book is classic algorithm book and I put it on my bookshelf near Knuth's volumes.