For the next two months, there is a special offer from Peter Pig.
Titles include such classics as Hammerin Iron (ACW ships), Square Bashing (WWI battles), AK 47 (modern Africa), and PBI (WWII).
Peter Pig rules all have a narrow time period focus. This ensures the things that mattered in that period are reflected well in the rules.
The PP website contains descriptions of how the various sets. In addition, the playsheets are free downloads. Marvelous.
The offer is that if you buy four rulebooks, the least expensive one will be given to you free.