Other than Charlie Chan Returns, I've not read any other stories outside of the Biggers' Canon.
With regard to "Returns", my recollection is that I wasn't really impressed with it. Much like I wasn't impressed with the post Ian Fleming James Bond stories. The authors, in either case gave it a yeoman's try but the characterizations of Chan and Bond seemed over the top, as if the authors tried to make each an hyper exaggerated version of their former literary selves. I may have to go back and re-read it and update my thoughts on it.
I do have all three of the Whitman "Big Little" and "Better Little" books. I have not read them as mine are in collectible condition and as such those books are not for reading. I do recognize the irony in that.:joy: Having said that they are essentially comic books illustrated by Alfred Andriola (sp?) who did the regular newspaper comic strips. Have not looked at them in a while but I'll pull them out of the vault :joy: and report back any interesting info or tidbits.