I read two Nancy Drew mysteries, The Haunted Showboat and The Clue of the Black Keys. Both go on the keeper list. I was waay too entertained by all the uses of the word "gay" in Showboat (yes, in the meaning of "happy"), because my brain kept casting it in the MODERN sense of the word "gay", with lines such as, "Oh, Nancy, but we've planned such a gay excursion!".

Looking back on it, "George" was dead butch...

I mostly remember two things about those books, that every chapter ended on a cliffhanger and that the solutions usually depended on sheer coincidence. E.g. Nancy is able to solve Main Mystery A because, luckily, information from Subplot B was fresh in her mind at just the right time. But I adored them when I was 12.