I recently finished reading SSH, The Secure Shell, The Definitive
Guide, by Barrett and Silverman over at O'Reilly. This book is
exacly what the title says, it's a definitive guide to SSH. It covers
installation and use. It incorporates SSH usage in a semi how-to
fashion but it also contains what How-tos would leave out. It
describes the how and the why related to protocols, procedures,
programs (scp, sftp...) and configurations. Through out the book they
discuss SSH1, SSH2 and OpenSSH (less) and a comparison of what one
SSH version has over the other. It covers aspects like Installation
and configuration, X11 Forwarding, Securing IMAP Auth and many others.

This book covers both the server and client aspect of SSH and I
would recommend this book to anyone who would like an in depth
look at SSH.