Scalability Rules: 50 principles for scaling Web sites, by Martin Abbott and Michael Fisher, is a concise primer on the basics of building scalable Web applications that can accommodate incredible growth rates. Packed into a paperback about the size of a Stephen King novel are 50 simple rules for dealing with complicated systems. Abbot and Fisher's approach provides the quick, high-level overview that managers need, the depth that developers want and everything in between.
When I first read the title, Scalability Rules, my mind tricked me into thinking it ended with an exclamation point (Scalability Rules!). While it's certainly true that scalable systems are pretty awesome, this book actually provides solid rules for building scalable systems. Abbott and Fisher have provided carefully worded explanations for what the rules are, why they make sense, when to use each rule and how to go about applying it.