Budget title with some bugs, but lots of fun for casual historical strategy buffs and worth the $20 price tag.
Basically it's similar to a cheap port of the old PC game "Centurion" on the DS - you march around one of several scenario maps, conquering cities with an army stack or three of legionnaires, auxiliaries and skirmishers (a shame that there is no regional map of the European and North African lands around the Mediterranean), alternating negotiating with and crushing (or, if you screw up, getting crushed by) the various city-states and tribes run by the AI. There is an ingenious mechanism for developing each city you have, where you can decide whether to optimize it for production of food, mined metals, lumber or troops (heavy or light infantry, archers or cavalry) and a tactical battle sequence, entered in whenever two opposing armies meet, where the player is prompted for a battle layout of his troops. Once a tactical battle is initiated the player loses control of the proceedings and gets to watch it unfold - not as much fun as having some sort of input, but given the DS handheld's limited processing power probably the best option for the programmers. Realism isn't all that great (having praetorian legions in the Italian peninsula unification scenario for example), but still quite exceptional for a beer-and-pretzels video title.
Along with the various strategy scenarios in various operational theatres there are four amusing little minigames - a sudoku game with Roman rather than Arabic numerals, a picture puzzle game where the player slides block around, a quiz game and a city hunting game, where the player has to find place names on a map while a timer ticks off. I particularly like the sudoku game, and all four of them are worth kicking around with a bit if you're too short for time to play a scenario to completion.
There are a few problems, and one nasty bug I ought to warn people about. First off, there's only one save game slot - if you want to save your game, you have to lose whatever you saved before. Also I must say that there have been occasional hangs and crashes during play - once at the very beginning of a scenario - so I'd suggest saving you game fairly regularly. The game seems to operate at the very limits of what the DS is capable of, so there are some minor issues with load times (sometimes lasting a few seconds), but nothing at all compared to what I'm already used to with my PSP. DS players however aren't used to this sort of thing, so fair warning.
All in all, I'd have been willing to pay $30 for this game and not feel cheated. It actually sells for $20 new, however, and is a great deal at that price (thus my higher score). Given how much fun this game is, I'm looking forward to getting "Military History Commander: Europe at War" when Slitherine makes a US release - WW II is much more my bag, although kicking it around with Roman troops isn't all that bad either.