i don't know if this has been posted before, but it is a good link to thousands of free circulars/books online. some busted links there but i did find quite a few good ones. free-book.58search.com -- free online books (http://free-book.58search.com)
e.g. book AS/400 TCP/IP Autoconfiguration: DNS and DHCP Support (http://free-book.58search.com/htmlpage/ebook-657762-879.html) written by Ibm.

site sucks