Jan,
Creating 9 different areas might be hard to manage, therfore I
propose that you may want to simplify this by clustering the remote sites
into provinces/states. A book that my collegue and I have been reading in
regards to our OSPF network design has been the Cisco - OSPF Design Guide,
or Designing and Implementing an OSPF network - Cisco.
Regards
Simon
Might also start with the OSPF Design Guide on the web:
<http://www.cisco.com/warp/public/104/1.html>
Then move on to the great books mentioned. I am partial to Halabi, but to be honest, I have not read the whole Moy book, and his name is on the RFC.... 
If the sites are reasonably close together, you do not need that many areas, but it might not be that bad an idea either. If the b/w is congested on the WAN, you'll probably wanna keep the areas.