The John Lennon Letters was published earlier this month by Little, Brown. New York reprinted a few from 1971, the year after the Beatles broke up (click to enlarge).
"Yoko...never, but never wears clogs
(or anything resembling clogs...!)"
"When people ask me questions about
'What did George Martin really do for you?',
I have only one answer, 'What does he do now?'"
"Dear Linda and Paul,
I was reading your letter and wondering what
middle aged cranky Beatle fan wrote it."
"Yoko's been an artist before you were ever a groupie."