The version 66.0 was a 165 MB app on an iPad Air 2 (64-bit). It was a monolithic app with it’s main binary being more than 100 MB.
The version 87.0 is now available: 253 MB on the same iPad Air 2 with only 64-bit code. In just 6 months, the Facebook.app size grew by 88 MB! More at Timac.
The Facebook app is shocking in terms of size, battery use and general terribleness. Best way to avoid all of this is to set up a home screen shortcut to the Facebook site. An even better way is to not use Facebook at all.