In 1961, Ivan Chermayeff designed and illustrated Sandol Stoddard Warburg’s Keep it like a secret (Chermayeff and Warburg had previously collaborated on The Thinking Book in 1960). The charming title, with its childlike connotations, was later appropriated by the band Built to Spill for their 1999 album. Sadly, we only have the jacket, not the book itself, but I did discover another version of the jacket out there.