There are other games where you can build your own fortress or castle, but Fortnite aims to create a system that combines ease of use and flexibility to let the player build on the fly. Sure it's a plus to actually plan out your structure from time to time, but if you would rather just go out and start building, Fortnite wants to accommodate you.
Fortnite is a big departure for Epic Games, the studio that is synonymous with Gears of War and the Unreal franchise, but I'm all for it as long as the execution and sound design from their Gears Series comes along for the ride. The game has a certain fun and carefree charm about it, and the gameplay looks chaotic but fun. It all comes down to how smoothly the on the fly building mechanics work, and how loose the combat is. In the gameplay footage you can see some of the combat, and while it looks fun it does appear to still need some tightening up. Hopefully there are some long distance weapons in play as well, as I can't wait to build myself a giant sniper perch, only accessible by a door which leads to a bridge which leads to another tower which has access to my sniper tower via carrier pigeon.
No mention of the pigeons yet, but peep the trailer (above) and some screens (below), and if you're interested (and have a PC) you can sign up for upcoming alpha access now.