FORMAT-E-EXPONENT-SIGNThe top of page 393 says, "Next, either a plus or a minus sign is printed, followed by e digits ... [decimal exponent]"
Later on page 393 we see, "If all of w, d, and e are omitted, then the effect is ... [like prin1].
Page 366 [presumably where prin1 is defined] doesn't explicitly say that the plus sign is omitted from the exponent, but all the examples (and usual practice) indicate that.
So the posssibilities are:
A. "1.0e+0" B. "1.0e0"
The first reference implies that A is correct, the third reference implies that B is correct. The second reference implies that A and B are the same.
This would cause the language on page 393 of CLtL to to change:
"If all of w, d, and e are omitted, then the effect is to print the value using ordinary free-format exponential-notation output; PRIN1 uses a similar format for any non-zero number whose magnitude is less than 10**-3 or greater than or equal to 10**7. The only difference is that the ~E directive always prints a plus or minus sign in front of the exponent, while PRIN1 omits the plus sign if the exponent is non-negative."
(format nil "~E" 1.0) => "1.0e+0"
PRIN1.VAX Lisp all print the plus sign as in the test case above. Apollo DOMAIN Common Lisp (version 2.10) and Xerox Common Lisp produce "1.0", which is wrong because it includes no exponent at all.