Some googling shows that member of the MAA and poet Ayshhyah E. Khazad (1944, Kalamazoo, Michigan) (aka Asha Khazad, aka Gimli Khazad, born John Pilaar) has a degree in mathematics from Western Michigan University. He participated in the Putnam competition in 1964, when he was a sophomore. Lang's book was published in 1966. The material covered there is rather elementary so it seems plausible that he would have been able to proofread Lang's book for him. He might have helped Kenneth Ross too, as another Gimli Khazad is acknowledged here.