Many assembly language books have gone out of print, but a great deal of assembly language information can be found on the Web. I include a number of sites that were current in early 2000 in the following list. Web addresses change or go bad on an aggravatingly regular basis, so if you can't find one of these sites, assume first that it's been moved, and only after some unsuccessful effort with the search engines, assume that the site is gone forever. (And for some things such as NASM, you can almost assume that it's been moved. Software as potent as NASM doesn't just disappear!)
The NASM home page: www.web-sites.co.uk/nasm/
The ALINK home page: http://alink.home.dhs.org/
The NASM-IDE home page: www.inglenook.co.uk/nasmide/
Linux assembly language page: http://lightning.voshod.com/asm/
Jan's Linux assembly page: http://bewoner.dma.be/JanW/engl
The 80x86 Assembly Pages: www.fys.ruu.nl/~faber/Amainl
These are the best pages I've seen, and they've all been around for a while. You'll find links pages on some of them that may direct you to newer Web sites that don't exist as I write this. The Web is a living organism, and you never surf the same wave twice. Keep both eyes open, so you don't miss anything!