Facebook released their new official app for window 8.1( Launched in October 18, 2013). What you are expected in facebook apps it contains like status updating, photo sharing, likes and comments notification etc
Features:
Friends show at side with their Snap, even using other apps
Get notified likes and comments on your photos and status
Sharing facility of Status and Photos
Group Conversations and Chat facility
Size:10.5 mb
Supported Processors: x86, x64, Ram