The Sesame Street Sign has the 'CTW' (Children's Television Workshop) initials on it. 'CTW' backwards
is '
WTC'.
Sesame Street is an anagram of 'Tears seem set'.
So we have:
WTC
Tears seem set
'
Monsters on the Loose' is an anagram of '
Oh loss! Enter Set's moon'
WTC
Tears seem Set
Oh loss! Enter Set's moon.
These guys allegedly worship the God Set, don't they? Since the moon on the book cover looks a bit like an eye, maybe that's Set himself looking down on what's going to happen
EDIT: Even weirder, and slightly more serious...this book is for the month of October 1976. Assuming that's October 1, 1976, do you want to guess how many days it was until 911?
9111.