There are a few decent concepts in the game, but they aren't enough to make it recommendable.
Heaven & Hell is a strategy game that plays on the you-are-a-god theme in the same vein as Black & White and Populous. As a god, your goal is to convert followers to your side by impressing or intimidating the local population. While some unique gimmicks and solid gameplay have made other god games fun to play, these elements are curiously absent from Heaven & Hell, leaving it a short, and otherwise dull, experience.
There are two sides in Heaven & Hell: good and evil. It's not surprising that these are the warring factions in a god game, but what is surprising is that both sides are, more or less, exactly the same. There are, of course, palette swaps and a few different spell names, but the two sides are, nonetheless, functionally equivalent. So it makes no difference, whatsoever, in picking your sides. It's not as if you have this problem when playing the campaign--as you can only start off on the good side. Once you finish the good campaign, you can move onto the evil campaign. Since both sides are carbon copies of each other, you may wonder what the point is in playing another campaign that's virtually identical.
The core mechanics of Heaven & Hell are pretty straightforward. Each map has a set number of cities with inhabitants. Each village has an overall "belief" in you, and each villager has a personal belief rating that you must influence by using a variety of prophets that you create from existing believers. When villagers' beliefs are high enough, you can convert them to your side by using the main prophet. There are other prophets who act as aids to the main prophet. One prophet recruits soldiers--soldiers who will fight enemy prophets and bully nonbelievers--while another prophet builds structures to attract villagers.
Your main resource in the game is mana. You gain mana by having followers and by converting houses into mana producers. Mana is used to cast spells and to upgrade houses. Mana is also used to cast god powers, which you can use to help sway the soon-to-be followers. You can call down lightning to smite enemy prophets, or you can create an earthquake to damage enemy facilities. You can also pat villagers on the head, when operating on the good side, or you can smack them around when on the evil side. This is actually the only major difference between the two sides. It seems kind of strange that the good side still uses soldiers to intimidate villagers, and that's one of the early disappointing aspects about Heaven & Hell.
Heaven & Hell just doesn't have enough to it to make the game fun to play. There are a limited number of god powers you can use, so you don't have too much direct control over the world. You must, therefore, rely on your prophets to influence the world. Each prophet has a couple of uses, but some of the prophets aren't useful at all. For example, the spy prophet can camouflage himself as a bush and sneak into a base. However, since you can see the enemy prophet camouflaged as a bush--and since you receive a warning whenever one steals your mana--the spy prophet is essentially rendered useless.
Controlling the few useful prophets in the game becomes a chore in itself. The game has a left-click interface, whereby left-clicking both selects and gives orders. So if you're trying to select a new prophet, you may inadvertently move the one you've already selected. Right-clicking deselects units, but that button also calls down god powers. So if you had lightning selected, you may accidentally electrocute your own followers instead of deselecting a prophet. Pathfinding in the game is pretty bad as well. Prophets will gingerly walk through opposing towns, and soldiers will often walk past moving targets before reacquiring them. It makes combat even worse than it already is.
That's not to say that there aren't some good ideas in the game. You can choose to have a limited, active role in taking over a village. Strong believers of the opposing side will throw rocks at your prophets, so you'll need to combine a few of them to succeed in converting such strong and resistant opposition. If you prefer, however, you can pick up rock-throwers and dump them on the other side of the map so your prophets can perform their jobs without harm. If you're in a pinch for mana, you can pick up your own followers and dump them directly into heaven or hell. You'll be rewarded with a small amount of mana, but the "juiced villager" is replaced by a child. A child cannot be turned into a prophet until he or she grows up--and then becomes easier to influence and convert. There is also a day/night cycle. Spells cast in the nighttime cost more, when on the good side, while spells cast in the daytime cost more, when on the evil side.
The AI is a pushover--even when set at a difficulty level of "hard." It will attack the same village over and over again. Your main strategy in the game is to upgrade several buildings in one village to "motivators," which raises the default belief of the villagers. Your followers will eventually become those fanatics who throw rocks at enemy prophets. You can then leave that village to its own devices, as the computer will constantly send in its prophets--only to lose them. You can then leisurely complete the mission's goals.
Skirmish mode plays exactly the same as the campaigns, but you probably won't want to even bother. When you start a game, all of the villages are neutral, and you can see where the computer creates a prophet. You can then create your own prophet in the same city to prevent the computer from converting anyone. The computer isn't smart enough to use the "pickup" god power to move villagers into its preaching range, nor is it smart enough to move anyone who's listening to your own prophet's sermon. Sometimes the computer just sits there and doesn't do anything during a random game. You probably won't find much of a challenge in multiplayer, either, as there doesn't appear to be anyone playing this game online.
There isn't much to the graphics or sound that will keep you playing the game. It's colorful and seems like it could be a good-looking game, but the unit animations are substandard. Villagers don't really do anything, other than just stand around. There are graphical glitches in the game as well. There are cutscenes between missions, but the videos stutter, so you'll probably skip them. The background music is pretty good, but the rest of the sounds aren't notable.
It's too bad that Heaven & Hell has so many problems. God games need to be especially well designed and fun to play since you don't have direct control over what goes on in the world. You must, instead, watch as your will is carried out by other characters. Unfortunately, this is Heaven & Hell's weak point--there's not much to do or see. There are a few decent concepts in the game, but they aren't enough to make it recommendable.