Jim Gray, Pat Helland, Patrick O'Neil, and Dennis Shasha. The Dangers of Replication and a Solution. ACM SIGMOD Record (25)2, 1996. Also in Red Book (3rd ed and 4th ed). [pdf]
This paper is relatively straightforward. My main comment is that you can skip all the equations. Instead, as you read the paper, try to think about the challenges of replication and the differences between the various replication techniques.