David Hows & Eelco Plugge 
The Definitive Guide to MongoDB [PDF ebook] 
A complete guide to dealing with Big Data using MongoDB

The Definitive Guide to Mongo DB, Second Edition, is updated for the latest version and includes all of the latest Mongo DB features, including the aggregation framework introduced in version 2.2 and hashed indexes in version 2.4. Mongo DB is the most popular of the ‘Big Data’ No SQL database technologies, and it’s still growing. David Hows from 10gen, along with experienced Mongo DB authors Peter Membrey and Eelco Plugge, provide their expertise and experience in teaching you everything you need to know to become a Mongo DB pro.