The rules are quite clear, and is in many ways very similar to Risk. You begin with up to 7 cities under your control, drawn at random. Each turn has 3 phases:

Firing and exploding missiles
Adding armies to the board
Moving and Attacking, building missiles, reconstructing

Missiles, obtained through successful attacks, are fired. There range is determined by how many missiles are interlocked and damage is done in the area it lands and the surrounding areas. All become devastated and units in those areas are lost. Missiles can trigger other missiles in the area, thus causing a chain reaction.

Extra armies are claimed depending on the number and type of regions controlled, for example, 1 extra army for every 2 urban regions or 1 extra army for every 4 mountain areas controlled. These units are then added to your empire.

Armies move into adjacent areas, but must leave at least one unit behind. Moves and attacks are done any number of times.
Combat uses the die in a unique way. The attacker selects a number not greater than the number of armies on the attacking region. The defender then has to guess the number. If guessed correctly, that number of attackers is removed. A wrong guess results in a missile being gained in that empire and a defender being removed. If this removes all defenders, the number of armies on the die must be moved in.
Simple, but effective.

SUMMARY:
I've played this many a time, and always thoroughly enjoyed it.
IMHO Games Workshop made a mistake concentrating on just one product, but then I've never liked Warhammer or its numerous spinoffs.

Review by Brian