Rome Total War is what you get when you combine an awesome turn-based strategy game and the best RTS game ever made.
In Rome Total War you are given the opportunity to conquer the known world using huge armies (forget the small scale battles of the RTS games and prepare yourself for battle with hundreds or even thousands of troops, infantry, cavalry, catapults and even chariots and heavy war elephants. The amazing detailing will completely change your playing experience. Soldiers are affected by whether, by terrain, by their morale (which is affected by the surroundings, for example, if your general dies or your soldiers are facing war elephants, they will break more easily and they will retreat after a short fight), by their exhaustion and even by the amount of soldiers left in the unit.
The battles are very realistic, let say you are fighting a phalanx, frontal assault will be a very bad idea (especially with cavalry) but attacking from the flanks or the rear will leave them no choice but to fight with their swords in which case they will be easily destroyed. But except of amazing battles RTW provides amazing city and army management. Will playing one of the three playable roman families you will struggle with the senate's missions (which are not mandatory but if accomplished the senate will reward you) you will need to conquer and defeat your enemies. When you will be popular enough among 'the people' you will have the chance to start a civil war and defeat the senate and the rest of the roman families conquering Rome and becoming emperor of the roman empire.
Managing the cities is extremely important, while making money in order to build your forces you can't increase too much your taxes because that will lead to anger among the citizens of your cities (also squalor doesn't help too much) and if they get too angry they can revolt and take your city. different buildings are responsible for different things, some buildings are suppose to increase your income, some are military buildings and some will keep the population happier.
Diplomacy is also important (although not very realistic) while trade rights will increase your income, military access is important if you don't want that a certain faction will declare war on you if you just want to pass your armies through its territory.
Family is also important (like in real life), all males that are older than 16 become generals in the army and they receive a whole bunch of bodyguards. You will be asked every now and then if you want to adopt a "son", he will marry a women in the family and become a general.
To sum up, RTW is a great game, some unrealistic features here and there but that doesn't change the fact that Rome Total War is the best game ever made so far. It doesn't matter how much it will cost, it will be worth it, so go to the closest video store and buy the game.