What makes a middle grade book one grown-ups will like?

I'm currently working a list for the Barnes and Noble kids blog of "recent middle grade books adults will love."  As usual, I thought at first it would be but the work of moments, but then I realized that I really should read all the best MG fiction published so far this year so I could make a really good list.  And then I realized that perhaps I was not quite the best person to make such a list, because of liking middle grade more that adult fiction as a matter of course, and so therefore finding the mind of the "adult fiction reader" a strange and unfamiliar place. 

There are some commonalities, of course.  Good books, whatever the age of the target audience, need to have good writing (I'm a vivid description sort of person myself), good characters (who act believably and make a place for themselves in the emotions of the reader) and interesting happenings (that don't rely on contrivance.  My sister, also a children's book reader, just read one in which an orphan and a pair of seals are dumped outside the same house on the same night by two different people.  She just couldn't believe in this coincidence enough to enjoy the book.  Although if people are going around dumping pairs of seals all over the place, perhaps a house that already had a baby orphan outside it would appeal as a seal dumping ground...). 

But the thing is, middle grade books are in fact not written for adults, and a mg book can have all the things mentioned above in it (except the seals) and still not appeal to grown-ups.  At least I guess that is true, and certainly books that rely on fart jokes aren't ones I'd recommend to an adult.  The middle grade books that don't work for me tend to be ones that have too much Wild Excitement and zip madly from one such excitement to the next.   The ones I love have excitement on a small scale--the girl finds the garden, and sees the plants are growing.  Some weeding ensues.  In any event, if you ever read in my reviews that a book "should appeal lots to its target audience" that means I didn't personally like it.  If I like a book, I say "I liked this book lots and lots" or something equally subtle.  

My doubts about my ability to predict which MG books adults will love are strengthened by the fact that I have been underwhelmed by books that adults have raved about.  The One and Only Ivan, for instance, just made me feel manipulated, though I was of course sorry for Ivan.  I take a little comfort from the fact that the adults who picked this year's Newbery Award winner, The Girl Who Drank the Moon, picked one I liked lots too.  I would include it on my list, except that it's no longer all that "recent" and it doesn't need an extra boost.

So in any event, here I am, frantically reading book after book with dead or dysfunctional mothers, and lots of mg speculative fiction that is fun but maybe too much "fun" and not grown-up enough? A children's book blogger, when thinking about a book, will have two trains of thought going--"what will kids think of this book" alongside "what do I think of this book"  (sometimes the trains collide).   Adding the third line of thought about "will grown-ups like the book for their own reading pleasure" is not something that comes as easily, because I have been a kid, and I love MG, but I have never been a committed reader of adult fiction (except of course for Dorothy Sayers, Mary Stewart, Jane Austen, and D.E. Stevenson).  Most grown-up fiction leaves me cold, mostly because it takes the books too long to get to the point, and the characters aren't likable, and then endings aren't as nicely resolved.  But I feel no desire to offer a list of children's books with those characteristics.

So getting to my own point--the books I like best aren't the books I'd necessarily recommend to your ordinary grown-up person, and I'm feeling flummoxed.  I have only one realistic one so far that I'm sure I'm going to include--Train I Ride, by Paul Mossier.  Which isn't a book I'd universally recommend to young readers.  It does what it sets out to do with no padding and it's a compelling story, but now I'm wondering if maybe the reason I liked it was the very small subplot elements of the main character finding ways while on board the train to get food which felt a bit like one of those fun survival type stories that I like very much......And I can't put that in the B. and N. post because it will probably just make the grown-ups look at me oddly.

It would be much easier to do such a list post for YA.

Please share suggestions and thoughts!