So the author is Richard Quittenton, he used the name Roland Quiz as pseudonym. His book 'Giant Land' tells a adventure of Tim Pippin, I'm not sure if the stories published on Young Folks are the same as the book or new ones. But apparently it was a really big saga, this edition says "end of book twelve of Pippin adventures' . I did saw some people saying the book was a influence for C.S Lewis, as he and Tolkien were friends, it really isn't a stretch at all. It's a pity we have only one edition here. I didn't find nothing else anywhere.
Link to the book:
Young Folk's Tales 198