There's a book (and, if I remember, a sequel, though it could have just been a 2nd part of the same book) I read in the 1970s, that probably dated from at least a decade or more earlier, that I've never been able to identify or find again.
The story was about a young alien named something like Martin, Marty, or similar, who comes to Earth, and goes camping (and/or joins the Boy Scouts) with the protagonist young Earthling boy. The sequel, or other part, was about Martin/Marty/whomever returning the favor by inviting the boy back to his home planet, where they go to a perfectly-reconstructed campsite that is otherwise located in the middle of an empty wasteland. I seem to recall that there were a lot of color illustrations.
Any help would be appreciated!