Proc fs Guide

Hi, Pardon for the newbie question, but since this is newbie forum anyway, here it goes Is this guide http://buffer.antifork.org/linux/procfs-guide.pdf (2001) updated (or outdated)? Is proc suffering any movement? I heard the prefered way to comunicate is sysfs, but I am working on a dated embedded environment and sysfs is not present. Btw, I am into that because I need to know the overall thread count. Greetings!