Last year, New York Public Library staffers discovered a lost treasure:  Nearly 6400 old note cards containing 20th century librarians’ reviews of the children's books that filled the library’s stacks.

The review system was never intended for public consumption. Instead, it served as a tool for intra-office dialogue. "It was just a way for staff to say 'here's what I thought of this book,'” says Lynn Lobash, manager of Readers Services. “And then other staff could come and look at the book and see what their colleagues had thought and decide whether they want to use it in a story time, or for whatever it was.”

Archivists have since stashed the reviews away for safekeeping, but not before the library’s delightful Instagram feed shared some highlights. Here are our favorites.

1. Tales of the Unexpected, Roald Dahl

2. On the Way Home, Laura Ingalls Wilder

3. The Outsiders, S. E. Hinton

4. Forever, Judy Blume

Two completely different takes on Judy Blume's "DIRTY TEENAGE NOVEL" Forever. #reviewsontues #nypl

A photo posted by The New York Public Library (@nypl) on Feb 25, 2014 at 4:52am PST

5. A Wrinkle in Time, Madeleine L'Engle

6. Jurassic Park, Michael Crichton

"Safety precautions fail, the animals escape, and the main characters escape one trap after another." #reviewsontues #nypl

A photo posted by The New York Public Library (@nypl) on May 20, 2014 at 4:54am PDT

7. The Grox And the Eugene, David Perry

What's so confusing about boxes of Groxes?? #reviewsontues #nypl

A photo posted by The New York Public Library (@nypl) on May 28, 2014 at 5:11am PDT

8. Green Eggs and Ham, Dr. Seuss

9. Fast Times At Ridgemont High, Cameron Crowe

10. Let's Go Logging, George Herman

11. Rikki-Tikki-Tavi, Rudyard Kipling

12. The Fifth Garfield Treasury, Jim Davis

Because, I mean, who can object to Garfield? #reviewsontues

A photo posted by The New York Public Library (@nypl) on Oct 7, 2014 at 5:46am PDT

13. Find Waldo Now, Martin Handforth

Tell the truth... How many times could you not find Waldo? #reviewsontues

A photo posted by The New York Public Library (@nypl) on Oct 7, 2014 at 10:45am PDT

14. The Snow Queen, Hans Christian Andersen. Two reviews of the book that became Frozen.

It's been a year since Frozen was released and the country is still gripped with snow queen madness! But how did the book fare with #nypl librarians? Review 2 of 2: "I must be getting old. Despite the many changes, removal of all religious elements, & additions of moralistic touches, a lot of effort went into art & text and I think it should be seen. Author constantly hypes up story with wolves howling, crows shrieking, flower garden lady walks on water, ill. show skulls and fanged demons. He's like a Steven Spielberg of pic. books. The robbers are arrested the goes to live with garden witch. He's trying to make it acceptable to modern parents: Gerda leaves a note for Grandma, is cogniscent [sic] of bad strangers, Robber girl is more introspective. Finn & Lapp women look like chubby kewpie dolls. Public will probably adore the melodramatic paintings. Interesting version. Rec. as additional purchase." #reviewsontues

A photo posted by The New York Public Library (@nypl) on Dec 2, 2014 at 9:03am PST

15. Hunches in Bunches, Dr. Seuss

16. Reading Skills, Marilyn Berry

17. Inspector Gadget in Africa, Sandra Beris

18. Sam and Violet's Birthday Book, Nicole Rubel