I once had a college professor describe dropping the -ly ending from adverbs, (using the adjectival form in their place) as the "Minnesota Disease" linguistically.
I don't remember how it came up, but Old Gray Mare and I got into a discussion of it while she was down, and everything I've read since has had an example or two of it in there!
In Nora Robert's third book of her Gallager's Pub series, Heart of the Sea, I was reading blithely along (note adverbial ending firmly in place, even though I was educated basically in Minnesota) on page 22 when I hit, "She needed to put them away proper, and stack up the gifts she'd bought, for she was a woman who couldn't abide untidiness for long."
If it hadn't been a library book, I'd have marked the end of "proper" with the "ly". Now, her characters can talk that way, and be realistic, but the NARRATOR should use correct English, and generally does in one of hers, as she's one of the better writers in her field.
On page 103, I read, "Leaning toward him, she caught his face in her hands and kissed him quick and light and friendly, as his grin had been." Well, one out of three, or should that one have been friendly-ly? With friendliness? Too deep for me!