A $35 book was published today with a really excellent chapter describing of the NoSQL ecosystem. If youíre interested in the NoSQL space, I highly recommend it (and you can read it for free from the links below):

NoSQL Chapter: http://www.aosabook.org/en/nosql.html

Rest of book: http://www.aosabook.org/en

Also, in case you havenít heard of the NoSQL Tapes, hereís a link to a bunch of high-level tutorial videos that explains the concepts behind big data to beginners: