Is the "with me" strictly implied, to make the English translation sound more natural? I don't see any words that could possibly translate as that, literally.
Yes, "with me" is not in the Klingon sentence. It is implied. It should be accepted if you wrote, "I brought these books from Earth". I think that the sentence translations are randomly generated by Duolingo from whatever was marked as best translation by the contributors so that was probably just one of several sentences that could have popped up for you.
qatlho', phuvtuo! Interesting that "with me" is not even in the translation showing on this page, although I must have seen it somewhere the first time around. Probably I did not use the clause "with me" and was given the sentence with it as "another translation."
I may have moved the "with me" from the "best example" to the "accepted translations". It is not needed and adds something to the English that is not strictly present in the Klingon. Often, when Duolingo updates, it also updates the translation shown on these discussions to that same "best example". When you first commented, the translation of this thread title probably did say, "with me".