Hi there Critical Miracle.
Thanks for posting.
The Nightmare War is a stand alone book. Everything a games master needs to get going is included in the book. With Campaign Gems we are avoiding adopting the model of releasing continuous splat books and additional sourcebooks. You can dive in with just the information in the book without feeling like you have to fork out extra cash on further books to get valuable information. We even included a 'whats really going on?' chapter (yup, its called that) so GM's know all the juicy details straight away.
Regarding d20 Modern - would it work better for character generation? Possibly, possibly not and its largely down to personal game mechanics preference. We felt the standard d20 System rules worked more than adequately for the setting, even if that setting was not fantasy and allows games masters with just the core D&D books to pick up The Nightmare War, flip through it and get a game going quickly.
As the section in the book describing what a Campaign Gem is states, we have a schedule of free releases underway for The Nightmare War giving additional value to the setting book. The first items are a half dozen PrC's and some additional equipment which will be released in the New Year through our website.
Thanks again for posting.
