For me, I loved Shadow Castle and The Westing Game.
After a long search, I was able to get both books for my children to read. It’s like finding a long-lost friend again!
Chippy Chipmunk’s Vacation (volume 5 of the Woodland Frolics Series). Chippy goes on an adventure and learns, through a series of mythological tales, such things as how the buffalo got their humped backs, how the Painted Canyon got painted, why aspens tremble, and so forth. I read and re-read that book to death when I was a kid.
I also loved loved loved the subject specific Golden Guides (like Reptiles and Amphibians and Geology). I had dozens of them, on all kinds of subjects (they were all science-related in my day; I don’t know if they still are). I don’t think those are very obscure, though.
Ooh! I loved the Westing Game. Completely forgot about that.
The movie sucked, though.
If it weren’t for your location and the reference to Kroger’s, I’d be asking if you were my brother. We had that same set (bought by my parents at the local A&P), and I read them cover to cover as well. That cover in the EBay auction took me right back, I’ll tell you. And then my folks bought us a set of Funk & Wagnalls’ encyclopedias, although ours was bought used and was a bit dated by the time I used it.
My username here is taken from an obscure children’s book, although one I didn’t read until I was an adult. I’m a huge fan of Theodore Sturgeon, and this was one of his favorite children’s books.
I just bought Shadow Castle before Christmas, but haven’t had a chance to read it yet.
The King, the Mice and the Cheese by Nancy and Eric Gurney. It’s about solutions that wind up being worse than the problems they were intended to solve, and really resonated with me later in life.
It’s very charming. I loved the imagery.
Just make sure you hide the butter. 
Cinnabar, The One O’clock Fox
The Wonderful Adventures of Nils, about a boy who flys off on the back of a large goose
Okay, that is tragic, tragic, that that book should be considered obscure.
Hmm … I always loved The Ship that Flew by Hilda Lewis. It was very hard to find a copy again after I grewed up, but it was worth it.
YAY! I had the whole set growing up, along with the big red encyclopedias (I “studied” art in my teens in spare time from those very volumes - no, not for dirty reasons, I really adored art - it inspired a lifelong love and appreciation for it). I loved those children’s books, and read them all inside and out until eventually, one by one, they were all lost or damaged.
Two years ago, I purchased the entire set off of eBay, and I read them over and over again. They are like long, long lost friends. Some of them inspired me to hunt down a few of the stories they only provided “teasers” for - like Miss Hickory. I love that book!
My favourite of all the stories in that massive collection, even today, is Mischief In Fez. Whenever my husband and I go to the zoo, I have to go see the fennec. I’ve named him Baha. 
The only thing truly missing from my new collection? A big jam stain on the pages of the story of The Three Bears in A B C Go!.
The Talking Parcel/Battle for Cockatrice Castle (it was renamed from The Talking Parcel :rolleyes: ) by Gerald Durrell.
No Flying in the House was the first book I ever read to my brother (I was 11, he was 5. We read together for years). I found a copy later at a library sale.
I’ve mentioned this one before, but “Sinbad and Me” by Kin Platt. Funny, incredibly convoluted plot involving, I dunno, hidden treasure, thugs, mysterious pasts, and architecture.
It’s apparently long out of print – on Amazon, the paperback is selling for somewhere between $80.00 and $200.00.
Oh My God! Mischief In Fez! That one illustration with the big one-eyed djinn! Hahaha!!! The other one that was always vivid was the Chinese fable where they open the trunk and all those hairy monsters come out - that illustration will be with me till I die!
Aren’t they the best books? So many memorable stories - I love Kiki the Ballerina, and the kids who open the store down by the road & sell sugar cookies and lemonade!
VCNJ~
Can I mention myself again in this thread? Are my books obscure?
Alas, I fear they are. That other pig with the arachnid friend kind of crowded me out.
The Perilous Gard won a Newbery Honor award in 1975, but I never see it on anyone’s “favorites” list, so I’m counting it as obscure.
I’m also counting it as my favorite book everrrr and I can’t tell you how many times I’ve read it since I first found it at age 11. Dozens and dozens of times. I still can recite passages from memory and still use phrases and bits of dialogue I picked up from it in casual conversation.
I’ve never met anyone who’s read it, but I’m sure that if I did, we’d be instant kindred spirits.
gallows fodder, I’ve read it! I recognised it instantly because I remember it was the first time I’d seen the name Jeffrey spelled “Geoffrey” and when I was reading my book report out loud in class I pronounced it “gee-off-ree” and lo, the class laffed and laffed.
Does this mean you love me a little?
Twenty One Balloons by William Pene Dubois
Mr. Revere and I by Robert Lawson
…and many more I can’t think of just now.
I am astonished to find that it’s back in print. Maybe it’s not as obscure as I thought it was!
Yes! 
Especially since you wrote a book report on it!
As a very small child, Ant and Bee.
And I’m not sure whether they’re obscure or not, but I loved the Zilpha Keatley Snyder Below the Root series.