I have a reasonable understanding of relational databases. I am not so sure about NoSQL databases. Though I have used mongodb in the past.
Can someone point me to resources to get a deeper understanding? How do I go about learning the trade-offs of choosing say a document store over a key value store. Also CAP theorem and related trade-offs. When is NoSQL better suited than relational etc.
The Little MongoDB Book might help. It doesn't answer all your questions but it gave me enough background (albeit MongoDB specific) to learn more. It's also a fairy short read. http://openmymind.net/mongodb.pdf
The Little Redis Book [1] might be better. Redis is easier to pick up and probably more useful as it's more complementary to existing database options.
I can't recommend enough the book Seven Databases in Seven Weeks by Eric Redmond & Jim Wilson. It covers the whole range of different types of databases, with just a little bit of theory (the CAP theorem).