[Katsunami]

Originally Posted by bobstro

Wasn't the update to "mostly harmless" all that the editors left of Ford's 15 years of research that he submitted after they left earth?

No; he has submitted it before he left the earth, because

Spoiler:

right in the beginning of the first book just after leaving the Earth, he already knows that "Harmless" will be updated to "Mostly Harmless" in the next edition of the Guide.

However,

Spoiler:

in book 4 Arthur gets back to Earth, which somehow miraculously still exists and only half a year or so has passed. After Ford finds out, he checks the Guide, and everything he has ever written about the Earth is now in it.