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If your employer uses a Hadoop cluster / ecosystem this book is a must. In simplest terms, Hive is an abstraction layer on top of Hadoop that presents the look and feel of SQL; it can also present the look and feel of NoSQL databases. This book discusses, in just the right amount of detail, how to put hive to good use and the important ways in which it differs from SQL and NoSQL technologies.
Well written, good book. However how fast Hive/hadoop is moving, I think this book will be out of data (already is in parts) soon. I'm assuming they'll come out with updated v2 of the book in the future.