Jay Kay Klein had extensive correspondence with authors, publishers, and science fiction fans. He also corresponded a fair bit regarding photography and amateur radio. Topics covered in the correspondence include inquiries to use his photographs and providing payment and credit lines for that use, issues regarding copyright and the use of his photographs without permission, convention matters (invitations, attendance, planning, and general discussions of cons), fandom and fandom concerns, publishers and publishing, photography, and amateur radio.

Unidentified correspondence has been sorted into two categories, TO and FROM Klein, and placed at the end of this series. The correspondence in these folders is unable to be attributed to a specific correspondent, either missing a name entirely or only including a common first name. There are also letter fragments.