Well, offhand, I typed both words into Wikipedia. After laughing rather hard at the first article, I came upon these.
Fuck has been the proper spelling as recognized in the Oxford English Dictionary since 1972.
Fook was a minor character in the Hitchhiker's Guide books written by Douglas Adams.
Also, we are grownups. You have to be of legal age just to even get into most horror movies. Many of us are also extremely attached to the word "fuck." We use it several times per day, if not per waking hour.
Which all leads to the common point that "fuck" is an awesome word. Please show our language some fucking respect.