[basetensucks]

I've found this book to be quite solid so far: http://shop.oreilly.com/product/0636920032175.do

I'm about a quarter to half of the way through and it's been interesting and quite thorough even though it's still a "beta" book. The content is a little high level so some familiarity with distributed systems principles is useful but the text is very approachable and easy to understand (so far).

I got it after seeing several recommendations in other HN threads so I'm not the only person that has found it useful.

[bogomipz]

I can also recommend this. Even in its beta form its still a worthy read. It feels more "rubber on the road" and less formalism. I'm looking forward to the finished book.

[cema]

Yes! I bought it a few weeks ago and am now going through it. A great overview of the topic.

[wsh91]

Another +1; tremendously useful even in its extended beta state. :)