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.
Personally, I have experience with MongoDB (school) and Cassandra (work). Although, I haven't had to really do enough with Cassandra to recommend any good resources on it. As for MongoDB, I have read several books on the subject and here are two (that I think) are really good:
Kyle Banker also wrote a good article called "MongoDB and Ecommerce", just to give some possible use cases for it.