I am getting more and more interested by the NoSQL technology and I can read several posts on SE about how it works and the different products available.
Here is a pretty comprehensive list of books, guides, and papers on NoSQL databases.
This is a tough question in the sense that there are several NoSQL databases out there, and they're all slightly (sometimes radically) different from each other.
An important concept to understand for NoSQL technology is that of Brewer's CAP Theorem, so I've provided a link to a good article on it. For a brief, graphical overview on the CAP Theorem, you should also look at Nathan Hurst's blog, a Visual Guide to NoSQL Systems.
I would also just search around on slideshare.net, there is some really good and useful stuff up there. After that, watch some vids of presentations from O'Reilly conferences and stuff like that. Absolutely I have found just pinging people on LinkedIn and getting their opinions was the most helpful.
I am at DataStax so I obviously prefer Cassandra but to each his own. If you want more info, feel free to reach out.
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