Alternative DNS Servers
Every once in a while, a technical book comes along that goes above and beyond what other books have done and becomes a standard reference in the field it covers. In this case, it's Alternative DNS Servers and its wonderful coverage of modern DNS.
This book is amazing. Jan-Piet Mens unbiasedly covers every modern authoritative and caching DNS server. This includes MaraDNS, tinydns, PowerDNS, and more that most people have never even heard of. Each server is given its own detailed chapter where you learn what sets it apart from the others and how to use it. But make no mistake, the coverage of each server is far from any simple tutorial or how-to you'd normally read. These chapters are packed with information that Jan could easily expand into small books on their own.
In addition to the several DNS servers covered, the amount of other DNS-related topics in this book is amazing. You'll also learn how to make your own DNS server and utility scripts with Perl, international domain names and how to make them work with your server, DNSSEC, nsswitch, DNS blacklists, and dynamic DNS.
I wouldn't recommend this book to people new to DNS. Instead, try O'Reilly's DNS and BIND or Apress's Pro DNS and BIND -- both are incredible books as well. But if you're familiar with DNS, maintain a DNS server or two, just want to widen your view of the DNS world, you would be a fool not to read this book.