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.
Comments
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.
[1] http://openmymind.net/redis.pdf
Thanks, will check this out.