If you want a quick summary just scroll down.

So while you are reading this I don't have many hours on the game but don't let this distract you. I played Heroes 5, 6, 7 - my dad played all the parts and he showed me this in 2011 when it came out. I played the 5th part for at least 3000 hours as I played it every day 2 - 3 hours for 3 to 4 years. This part fascinated me a lot but when I firstly saw the 6th part I was totally shocked, but in a positive way, the graphics were amazing. Back then there were no town screens but now there are some, the campaign was pretty good, and the units had in my opinion the best design out of those 3 parts I played. Every unit has a unique ability and/or stats and every faction is different to play. Well you might be afraid to buy this game as it has bad reviews, but you will probably see that this is because they cannot start the game which can easily be done by opening the game folder, disable full screen and start the game as an administrator. Don't worry the game will launch in full screen. You may as well see that the most positive review have much more hours than the ones who are negative, The reason for this is that you can't simply play Heroes 6 or any other Heroes part like a normal game you play. No, you have to understand how each faction is played. It’s not the same to play as necromancers and as stronghold, they have both different technics and with time you will start to master them. If you are into strategy buy this game but if you are one of those people who give up on a game if they don't manage to succeed a level on the first try don't buy it, you will rage. The campaign has, as far as I know 22 levels, with each taking about two hours. Don't get me wrong but you won't do them all first try, except you watch some walkthrough, and even if you do that you may lose, as the walkthroughs are not how you play, but how the person who uploaded it plays. Even on normal difficulty it could take you far more than two hours to complete a level, due to the strength of the AI.

Summary: The game is really challenging and has good graphics, it hard to master but makes much fun there is a skill system, good combat mode, and all in all very well done.