If you just want to learn the file system layout then they all are laid out somewhat similarly, at least for all the main directory structures. I'm not sure about SUSE but Red Hat has all their manuals on line from RH 7.x through Red Hat 9 (the last version that you could get a boxed set of):
http://www.redhat.com/docs/manuals/linux/
Worker is right though. At the basic level (kernel, file system, system apps (apache/php), etc) all distros are pretty much the same. At the middle level (package management) there are groups of distros that are similar. SUSE, Red Hat, Mandrake and a few others are all RPM based. Debian, Xandros, KNOPPIX, and several others are all Debian based (deb packages). At the highest level (desktop layout, custom management tools) they are all pretty much different. For instance, SUSE comes with a system management tool called YAST. Red Hat includes several individual graphical tools to configure each component. Some distros customize the look and feel of the desktop. For instance starting at Red Hat 8.0 Red Hat created a theme called BlueCurve for both Gnome and KDE and customized other things about each desktop environment to make them both be very similar as far as menu layouts etc.
Personally, I rarely use a GUI for doing anything other than surfing the web. Any system configuration I do at the command line level. When you understand how things work at a lower level and can configure them in this way you'll probably be quite happy with any distribution. I ended up just picking one way back when, after switching back and forth many times, and sticking with it, upgrading as new releases came out. For the most part I run all the Red Hat based stuff, from Red Hat 6.0 (yep, still have one of those running) to Red Hat Advanced Server 3.0, to Fedora Core 2 on the destkop. I also run Debian on a few machines (with SPARC and Alpha processors). But really I would be just as happy with any distribution for the most part. It's just easier for me to pick one and run with it.
So if you are really in the learning mood by all means install what you have and go through the book. You might want to also install some of the latest releases of a few other distributions so you can see how things are different. Things are different in Linux as you've probably discovered. When I first started with UNIX way back when I didn't like it. The more I used it and the more I learned the more I liked it. It wasn't long and I was to the point where I wondered how I ever got anything done any other way.
Good luck and I'll be happy to help you with anything you need help with.