Cranky.

John Lennon, like many geniuses, had a temper. Living in a time before email, texting and other instant forms of communication, the peace-loving rocker shared his often pointed opinions the old-fashioned way -- by writing letters. The newly published book The John Lennon Letters contains reprints of correspondence to fans, business associates and even collaborator Paul McCartney. Many project a strong point of view, bordering on caustic.

In excerpts secured by Vulture.com, Lennon saves his harshest comments for McCartney's first wife Linda, whom accuses of acting like a "middle aged cranky Beatle fan." Speaking of fans, he skewered one who dared criticize his wife: "Yoko's been an artist before you were even a groupie." In another, John claims producer George Martin took too much credit for creating songs such as "Across the Universe."