It covers the MapReduce programming model as much as an introduction to HBase/Bigtable concepts and a deeper look into the (Hadoop) distributed filesystem. Furthermore other Hadoop subprojects like Pig and ZooKeeper at Apache are also covered.
Although I hadn't read through all chapters in depth until now, I got a basic feeling of how the big players like Google or Amazon can handle the enormous amount of data they are dealing with.
This book is worth a deeper look and I recommend reading for everybody who is interested in alternative database techniques to SQL databases.
A very brief but good overview about NoSQL Database you also find at ref card at dzone.