Daniel C. Lynch and Marshall T. Rose, eds. Internet System Handbook. The Internet System Handbook is a collection of essays written by 23 Internet experts, including the two editors, plus Vinton G. Cerf, Stephen Kent, and John S. Quarterman. While published in 1993, all of the essays were written in 1992. As one would expect with a collection of essays, there is quite a range of writing styles and depth of coverage.
Some essays are very general, and accessible to a wide readership.
If you're one of those people who likes their reading to have flow and consistency, you may have a problem with this one. Then again, this ain't exactly Stephen King. One reason the book remains useful today is that little time is spent on discussing applications, although e-mail, FTP and Telnet are discussed at some length. The focus, instead, is on the foundations and architecture of the Internet. As someone who needs to understand how everything I use works, I find myself referring to this volume with some regularity.