https://www.humblebundle.com/books/unix-book-bundle

These are electronic (searchable) copies, not paper.

$1: Unix, sed & awk, lex & yacc, bash, linux pocket
$8: bash cookbook, classic shell scripting, GNU Emacs, vi and Vim, bash pocket, Unix for OS X, Unix Power Tools
$15: Essential System Administration, TCP/IP Network Administration, DNS and BIND, Network Troubleshooting Tools