Dark souls 3 is gameplay based game, so we do not expect fantastic story from these type of games. For this kind of games, it has acceptable story line but we can not compare it with story based games like Beyond: two souls. The whole story is, you are hero of the dark world and you should save this dark word with linking fire to yourself.
In this version of series, you have new mechanic that named weapon art. weapon art makes gameplay better than previous versions, some times camera is not in the good position ( for example it goes into the bush and i can not see the enemy). Combat technics and difficulty is well designed, actually they did great job in this aspect, you can be like tank if you wear heavy armor and shield and big weapon or you can be something like assassin if you equip yourself with light armor and double sword. Or if you into magic and do not like close combat be mage. you can upgrade your weapons and upgrade your abilities. This game has great level up system which allow you to level up your character with your playing style.