Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A reasonable beginner text

If you tried Nancy Lynch's "Distributed Algorithms" and only care about web apps, this might be the book for you. It's readable, useful for people developing web back ends, and up to date. However, it doesn't try to cover the complexities of general fault-tolerant distributed systems. Besides Lynch's classic text, I recommend Gray and Reuter's "Transaction Processing," a seminal text that should give you a clear idea of how to compose arbitrarily reliable systems out of unreliable components.