Why would "these books are interesting" be wrong?
That should have been accepted in a translation exercise.
If you have a screenshot showing the question and your answer, that would be extremely helpful in finding out what went wrong -- upload it to a website somewhere, please (e.g. imgur), and tell us the URL of the image.
It's really annoying that Duolingo limits the levels of discussion.
I was really referring to how it works in Klingon, so I can see how that was confusing. Here's a more accurate grammar breakdown:
In "These are interesting books," the adjective "interesting" is being used to directly modify the noun and form a noun phrase which is then used as part of the predicate, "are interesting books." We can do something similar in Klingon by placing the verb acting adjectivally after the noun it is modifying to get paqmey Daj bIH ("They are interesting books.")
In that English sentence we are also using the pronoun "these" and we don't have such relative pronouns in Klingon. You have to use a generic noun like Dochmeyvam or repeat the noun like paqmeyvam:
paqmey Daj bIH paqmeyvam'e'
"These books are interesting books."
Notice that a phrase like this is actually equating two nouns and that uses a special grammar (specifically, a pronoun-as-"to be").
Many words that are adjectives in English are actually verbs in Klingon. In English you still need the copular verb "to be" to equate a noun to an adjective (as in "These books are interesting"), but in Klingon, since the adjective is already an actual verb, no additional copular verb is needed and you just place the noun in the subject position:
"These books are interesting."
While I agree that the semantic intent of these two sentences is very similar in both languages, the syntactical structure is quite different, especially in the Klingon. And in a learning environment like this the syntax is as important as the semantics. Since there is a correlation of one specific English structure to one specific Klingon structure and a correlation of different specific English structure to a different specific Klingon structure, we insist that you maintain those correlations and we do not allow them to be mixed.
Hmmm, I can't reply to your message, jdmcowan (maybe too many levels of discussion?). I don't understand how "interesting" can be a verb. That doesn't seem to make sense to me. At least from common verbiage, I'm pretty certain that these two sentences are equal. But I understand that with translation it has to be exact. I just don't understand where that exactness is.