The only major differences between the 2 are that in RedHat 7.2:
1. Your compiler is actually going to work, unlike 7.0.
2. There's going to be some info about Linuxconf that isn't part of RedHat anymore.
3. RedHat now uses Grub as the bootloader by default instead of Lilo
4. 7.0 was based on 2.2.16 while 7.2 is based on... crap, 2.4.7?, maybe 9? anyway, the big difference is that one is 2.2.x series and the newer is 2.4.x. The old one runs its firewalling on ipchains, the newer on iptables. The book might not cover iptables.
That's just about everything I can think of that's a biggie.