We’ve all been there, yes? I believe I once did something like this to my brother. “What was that one book with some unidentifiable characteristic?” He figured it out, somehow, as I recall.
It turns out that these days,, there are plenty of websites that might be able to help with this. Much more at the link.
I will say, out of curiosity, I tried Big Book Search and Google to see if either would turn up a nonfiction book about animals I really liked as a child. I typed “Childrens book nonfiction animals green cover.” This did not yield any useful results, with all the results being picture books or books for very young children.
If you happen to know a child who is really into animals, the book I had in mind is The Burgess Animal Book for Children.
Here is the copy I have downstairs:
For reasons that are not clear, the current cover, visible at Goodreads at the link provided, shows a … jaguar … on the cover. Since all of the animals discussed in the book are North American, I am somewhat bewildered by this. Perhaps the publisher of the newer edition is under the impression that children cannot tell the difference between a bobcat and a jaguar. I assure this publisher, whoever it is is, that they certainly can.
Incidentally, the picture above is from Abe Books. They will sell you this copy for $124. But it’s a first edition. Modern copies are very affordable.
But it’s a good thing I knew what the book was called, because “green cover” did not get me anywhere.