He then had it returned and obtained another—a most instructive incident, since it proved conclusively to my mind that we were dealing with a real hound, as no other supposition could explain this anxiety to obtain an old boot and this indifference to a new one.
There are no more uses of "instructive" in the book.
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And very instructive.
Rick Yancey -- The 5th Wave
"Let’s table that thought for a second, because that’s instructive, the fact that you were aware of the groups, but didn’t seek them out.