I know what you're thinking 'This isn't dead island'. Of course not, but at its core, it's dead island. The fighting mechanics for instance, allthough improved, are dead island mechanics. It's still a new game though, they improved and changed a lot of things.
So what is improved? because as much as I liked dead island, we're 2015. I certainly don't mind a game with dead island style of play, but dead island wasn't perfect, not for 2015 anyway.
As you've certainly heard, they added something called parcours to dying light, which actually works extremely well and is a nice improvement. For those who've played dead island probably remember that it was sometimes a smart thing to run and jump to higher ground. Well this game greatly improves that mechanic, you can actually jump from ridges to ladder, rooftops and so on, if it's somewhat possible for an athletic parcours guy, you can do it. It does have some similarities with assassins creed in first person for climbing (but it's more realistic)
There's one falling jump, in the tutorial, that's not possible, well it's possbile but you probably wouldn't survive it. If I did a similar jump later in game (so not in the tutorial), I would have died, just like in real life. I didn't finish the game though, so I don't know if something this unrealistic (parcours wise) will return. Maybe they did it as a joke but in any case don't you ever try that jump in real life.
The overall feel of the engine is certainly better , while dead island had sometimes the feeling of being cheap while moving around, this game does not have that. You feel where the game is coming from though, but they made the engine a lot better. Moving around goes as fluent as ever and feels natural, even with all the parcours stuff going on. The combat mechanics feels pretty similar, allthough they are a bit more fluent than dead island.
The game still uses the same mechanics how you find quests, items, weapons and level up but of course some things are new or improved (like upgrading/repairing weapons without a workbench, upgrading parkour abilities, lockingpicking etc..). There is four player co op and there is a new system where players can invade others people games as a zombie. I didn't test this but you can disable this mechanic. Nighttime is also more dangerous than daytime, more gruesome creatures come out of the shadows then (hence the name dying light).
Graphics wise, the game looks better than the dead island games. Still, it is built on the same (or a similar) engine. A lot of objects, houses, plants, trees and textures will look quite familiar but not everything is reused. A lot of stuff is new and the new textures, objects, npc's, shadowing and lighting are better in quality. The blood and gore looks as good as ever.
Overall the whole game looks and feels a lot darker and sinister than dead island (no bikini beach babes here!). Dead island's cartoonish characters, fluo colors and comical atmosphere made the whole experience a little less horror-esque than it could have been. Dying light does no such thing though, not for the short time I played it anyway. Blood looks like real blood and the reality of this game is that a brain and flesh eating zombie plague is no picnic. Still, they saved some room for dark comedy though, this game is after all created by the same studio that made dead island.
As for the system requirements, they didn't lie... at least not for recommended settings. You might get away with lower than minimum for the gpu and especially for the cpu.