The Early Access version of the game contains the following, per Tripwire:

Three non-linear levels - The dark streets of Burning Paris, the ice covered Outpost, and a re-imagined version of the original Biotics Lab
Four perks - Berserker, Support, Commando and Medic classes
27 weapons - Ranging from shotguns to assault rifles to crazy makeshift hybrid weapons!
11 deadly and terrifying Zeds – All determined to destroy you
Seven playable characters – Including fan favorites Mr. Foster and Constable Rob Briar as well as a new female character – Ana Larive
One new boss character – Enter Hans Volter and his arsenal of devastating weapons and attacks
Mod SDK supporting custom level creation