Wow! THE THIRTEENTH PEARL did not age well and re-reading it just confirms that some childhood memories are best left without revisiting.
The book's main problem is that it was poorly edited. Grammar issues that should have been caught were not. A couple examples:
Plurals do not need an apostrophe. An apostrophe either before or after an "s" at the end of a word shows possession. In other words, the Cuttinis would refer to two or more people named Cuttini, and Cuttini's refers to something possessed by Cuttini.
A word showing relationship (mom, dad, aunt, uncle, etc.) is not capitalized when it follows a possessive pronoun (my, our, your, his, her, their). That means it should be "my dad" or "our aunt Gertrude" and not "my Dad" or "our Aunt Gertrude."
However, I think the real reason for the lack of editing and tightening up the story is that the Stratemeyer Syndicate, then the owner of Nancy Drew, the Hardy Boys, Tom Swift, and many, many more children's series characters, had signed a new publishing contract with Simon & Schuster for new books in various series. Moving to a new publisher would certainly kill any motivation I had to improve an inferior draft, so I don't believe my theory here is too far off. Had the proper editing been completed I don't believe the word "Asiatic" would have been used as Asian was already the more acceptable word choice.
(By the way, the original Nancy Drew series ended at book 175 and there have been various spinoff series throughout the years. As bad as I think THE THIRTEENTH PEARL is, books 57-74 (I think, though it could be book 73) -- also written by Stratemeyer Syndicate authors -- contain some better-written stories than those of the 56 published by Grosset & Dunlap, while featuring the same Nancy Drew as before. Starting with either book 74 or 75, books written by ghostwriters for new owner Simon & Schuster began to be published.)
Enough grammar and history!
There are better Nancy Drew stories than this out there. May I suggest THE CROOKED BANISTER or THE FLYING SAUCER MYSTERY? I suggest reading this one only to be a completist or to learn how pearls are formed when mankind aids in the process or to learn Japanese customs as viewed through a 1970s perspective.