a gang of kid mystery solvers, with one kid having a pet squirrel. The book was arranged in such a way where the left page was words and the right facing page a black & white illustration which contained a clue, very detailed illustrations similar to Where’s Waldo. From the 80s I think.
The Adventures of the Black Hand Gang by Hans Jurgen Press.
YES! Oh my god you don’t know happy you’ve made me!!! Been trying to figure this out for years!