Apache Administrator's Handbook is now available at your local bookstore, or on Amazon.com.
Although Apache 2.0 has been released for some time, Apache 1.3 will still be in widespread use for some time to come, and this book focuses mostly on 1.3. However, the things that you learn for Apache 1.3 will almost all translate directly to 2.0 without much change. When there are major differences between the two versions, AAH points this out.
This book does not attempt to be a comprehensive Apache manual. There is already one of those, at httpd.apache.org/docs, which is updated and improved on a regular basis. This is intended to be a companion to those docs, not a replacement for them.