A story that I continue from time to time, depending on when ideas come to me. I've got a lot of ideas floating around, and I guess I'll slowly get them down when I come to them.
The format of this story is not a book, rather I imagine it as a computer game, one that could fit into the Final Fantasy series.
In the last 50 years, humanity has suffered from a relentless attack by the animals (monsters) of the earth, called Gaia. The Department of Frontier Research and Defense, commonly just called Frontier, is a military organisation created to combat and research this behaviour. Originally a military branch of (and still technically under the direct control of) the Senate and the People of Lavinia (SPL), it has become the main military defense force of all countries in the United Countries of Humanity (UCH). This alliance was forged due to the relentless assault on all human civilization, resulting in most humans being driven back to an area of coastline known as the Medigaianean.
The reason humanity is losing this battle is that there is no such thing as gunpowder or carbon fuels, and so the overwhelming firepower of normal Earth militaries is unobtainable. Soldiers are still much like medieval armies, with crossbows being the closest thing they have to a gun. Mobile land artillery fire support does not exist. However, due to this lack of chemical energy, electrical technology is extremely advanced. Electrical counterparts have replaced most combustion processes (ie electric vehicles, trains, helicopters). Nuclear reactors are common place, and rail guns (using plasma rails) have been developed. Unfortunately these rail guns require a lot of power, and so cannot be made into field artillery. The Navy is the only source of fire support (as ships can have nuclear reactors and hence rail guns). This is why humanity has been driven back from inland areas, unable to effectively combat monsters until distances where naval fire support is possible. The indefensible inland settlements were overrun one by one, the remaining populace butchered, and the towns utterly razed to the ground.
There are many pockets of humanity living along the coastlines of the world. Trade still happens between them, though many have become isolated, forming into Unions.
There is no such thing as an air-force. Planes are unable to fire projectiles, and so are useless in combat applications, however they are used extensively as reconnaissance, along with satellites that have been fired up into the sky by huge rail guns. These enable civilian and military communication networks. Helicopters have been developed primarily by the navy as a mode of transport.
Frontier's soldiers are known as 'hunters'. Each hunter has a Head-up Display built into his helmet, and is in a fireteam directly monitored under satellite surveillance by an operator. Their skills, deeds and kills are monitored to give them a rank based on their proficiency. The main base of operations of Frontier is a ship, the largest one ever created, the UCS Hope, having a permanent crew of 10000. This boat travels between the regions of the Medigaianean to periodically reduce hostile animal populations in the region. Being Frontier's control centre, its callsign in radio communication is 'Foxtrot'.
Magic is a genetic evolution appearing in many animal species. Unfortunately, humans branched off in the direction towards superior intelligence to combat evolutionary pressures, whereas animals continued towards being able to control elements. Frontier has been researching human and animal genome compatibility to create humans with magical capabilities. The characters are their results.