NoSQL Distilled. P. Sadalage, M. Fowler

 This book seeks to give you enough information to answer the question of whether NoSQL databases are worth serious consideration for your future projects. Every project is different, and there’s no way we can write a simple decision tree to choose the right data store. Instead, what we are attempting here is to provide you with enough background on how NoSQL databases work, so that you can make those judgments yourself without having to trawl the whole web. We’ve deliberately made this a small book, so you can get this overview pretty quickly. It won’t answer your questions definitively, but it should narrow down the range of options you have to consider and help you understand what questions you need to ask.