It's not exactly rocket science is it?....oh wait, yes it is.
Kerbal Space Program is a game about building spacecraft and, unless you're very good at the game, watching them blow up which is currently in Early Access. In KSP you design and build your very own spacecraft/rockets and spaceplanes which you then use as you leave Kerbin to further the scientific knowledge of the humble kerbal. With a vast array of parts at your disposable it's daunting at first, well it's daunting for a while, but once you get the hang of it this game is a blast, especially if you have any interest in astrophysics or aerospace engineering.
KSP has four different game modes each of which I will give a brief description of.
First off there's sandbox mode. In sandbox mode you have no limitations and most importantly you have access to all of the parts right away, this is the perfect way for new players to get to grips with building and figuring out what works well and how the game works.
Next we have scientific mode. In scientific mode you have to generate science points from doing experiments in different places, e.g. the surface of Kerbin or low Kerbin orbit. Science points you earn can then be spent on new technologies in the tech tree which unlock new parts which help you to go to new places to complete more experiments. You begin with few parts which are basic so unlocking new technologies in imperative to progress.
Up next is career mode. Career mode is scientific mode but now with money and reputation to worry about. Money is earned by completing contracts, such as putting a part on your rocket and getting it to a certain altitude and then money is spent on parts for your rocket or spaceplane. Reputation is earned by successfully completing contracts, the higher your reputation is the better the contracts you get offered are. However, reputation can be lost through either failing contracts or losing kerbals.
Last, and probably least depending on what you like, are the game's pre-made scenarios. Ranging from tutorials on docking to the NASA redirect mission this game mode is what you would expect it to be, just different scenarios to try out, not much to say about this one.
+Graphics are pretty nice
+Lots of different parts
+The building menus are good and building is relatively easy, by easy I mean straightforward to use not easy to make decent vehicles
+A number of different planets and moons, each with different appearances and properties
+Good controls and useful hotkeys
+Good staging setup
+Endless possibilities of what you can make, from simple little rockets to huge spacestations in orbit around distant planets
+Reasonaly good physics but not perfect (I'll get to that later)
+Great modding community and adding mods is extremely easy
+Kerbals are nice little race and you can get attached to the more well known kerbals quite easily (I <3 Jeb)
+/-Very basic tutorials, this game really throws you in at the deep end
-Immensely steep learning curve, I'm 60+ hours in and I've only recently made it to the Mun (and successfully landed)
-The physics and controls for spaceplanes are pretty bad, spaceplanes have clearly been neglected in favour of rockets
An outstandingly good vehicle builder/sandbox game which is perfect for anyone with an interest in space, the related physcis or anyone who likes building vehicles.