If you want a cheap, and very long game that is generally good, then this isn't a bad choice.
If you are familier with the Heroes of Might and Magic series, King's Bounty will quickly feel familiar. You have five different troops in a certain quantity and you use those troops to engage in combat on a field of hexagons. Most troops have some sort of special abilities, like walking further once during a battle, being able to use bless every second round or split themselves into two units, dividing their health. Your troops have a base attack stat, defence, damage and health. In addition to attacking with those units, you get to use a spell once a turn, whether laying a trap, strengthen your troops, weaken your enemies or directly hitting your enemies with say a fireball.
While the gameplay do feel similar, I would rather call King's Bounty a heroes reimagening. For one thing, you don't have a castle to improve and you aren't supposed to conquer anything, just serve the King and search for Bounty - hence the name.
As I said, this is what the game feels like it is all about. There are just so many things to collect, that I'd like to make a small list for you:
Experience: Used to level up
Gold: Used to buy things.
Weapons: Change your stats and some lessen the leadership requirement for a certain kind of troops.
Other Gear: Same as with weapons. Some also make you receive more gold or expirience from battle or increase the effect os spells and such.
Other items: Some - like eggs, can be used to create a troop. Others can be sold and some are used in quests.
Leadership: Gained through finding flags or leveling up. Can also be increased by wearing the right gear. Determines how many of a certain troop you can recruit. If for instance your leadership is 12000, you can recruit 1200 peasants (leadership requirement 10) or 6 black dragons (leadership requirement 2000)
Scrolls: Contains spells, and you can either use the scroll to use the spell or learn the spell from it using crystals.
Crystals: Used to learn or upgrade spells
Runes: Used to upgrade your hero on three different talent tables, one for Might, one for Mind and one for Magic. The different skills on the Might table cost mostly Might Runes, but also Mind and Magic runes. Skills includes better stats, the ability to upgrade certain spells, increased experience from battle, increased strength of certain spells, less leadership requirement for some troops etc.
Mana: Used for spells, and throughout the land there are places where you can get your maximum mana increased. mana regenerates between combat.
Rage: Used for special attacks from four "Spirits of Rage" - once you unlock them. Rage is gained through getting attacked or attacking enemies. Between combat, the rage is slowly drained. Maximum rage can be increased like with mana.
As you ride through the land, you need to take on various quest. The main quests are for the king, and at first are pretty trivial matters, but after a while you are sent to make peace treaties and then to rescue the King's daughter who has been kidnapped. However you also take on quest for other people, involving fighting, collecting stuff or both. The team seem to have used a lot of effort into writing the dialogue (which is always just text), for those quests, and I even used to read the dialogue for a while. However, the story fails to deliver on many points. When an NPC told me that necromancy was forbidden and I discovered that one of the Skills on the Magic talent table was titled "Necromancy", I chose it, hoping it would effect the story in some way. It didn't.
King's Bounty is a very strategic game when it comes down to it. There is a limited amount of enemies in the land and there are a limited amount of treasures, making it important not to lose too many soldiers in a given fight, because you may not afford to replace them. There is also a limited number of most kinds of troop, which I find rather interesting. A shopkeeper may only have 56 snakes, so once you have bought and lost all of those, you need to find a new supplier of snakes or replace them with a different kind of troop. In the beginning, only peasants came in an unlimited supply, but then after some quests the king had several troops that I could buy in whatever quantity I prefered, and that made that aspect less important.
The troops range from animals, to several types of royal servants, to bandits, elves, dwarves, dragons, orcs and several mythical creatures. The fact that you need to go to specific places to recruit them ensured that a lot of my playtime was spent going back and forth between where my enemies are and where I buy my men once I've either lost some or gained leadership enough to buy more. I really wish they had done more to lessen the travel time. Sure it is nice to be able to fly from the dwarven castle to the royal castle, but for some reason I couldn't do it until after the peace treaty, which meant I had to go back and forth about twenty times before that happened.
The main problem with King's Bounty is that you progress so slowly. In most cases you can't afford to replace your team with local troops wherever you go, and replacing some often leads to your regular troops getting lower morale. You see my royal archers are picky, and they dislike being teamed up with pirates, spiders and zombies (whiny bastards). So since there are many enemies in an area and you practically have to do all the side-quests to be strong enough to stand your ground in the next area, it is going to take time.
Still there are many aspects of the game that I find enjoyable. Searching for riches is addictive, the combat system is fairly good even though it gets repetitve and the explorations is great up until you've seen each area so much you could turn off the game and paint it in great detail. One of the things I really enjoyed was that I was given large freedom as to the order I wanted to fight my enemies in. Ever so often I tried battling an opponent labeled "impossible" (which sometimes turned out possible) or a boss fight which was intended for higher levels. The most memorable one was defeating a spider queen that spawned litterally tens of thousands of spider children throughout the battle and in the end I survived with only two units still standing and the exp I gained was enough to advace two thirds of the way from level 15 to 16 (and to get this straight, you only get to about level 30 at the end of the game).
So in short, the game has a story that seems interesting at first, but doesn't quite deliver, it has a combat system that is good, though repetitive and an exploration aspect that is nice, but somewhat tiresome. Where it truly shines is at searching the land for treasure and making your character more and more badass. How much time you put into it depends on the difficulty you choose, how long it takes until you stop reading the dialogue and how much you travel to buy your men. According to Steam I spent 78 hours playing through the game once on normal mode. That is quite a lot for a game that at the moment is 10 dollars. For me it was a particularly good deal since I bought all three games in the series for 22.5 dollars during the Christmas sales.