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The book was about a man who would be surgically altered to investigate different planets, and live with the alien beings on them. He would learn about them, and their social/linguistic behaviours. On one planet he became a being that would curl into a ball and roll. On another, he became some type of lizard-type thing that had a pyramidal structure sticking out from it, the purpose of which he did not know. It's not a recent novel, I probably read it 25 years ago. There were at least two or three different life forms he was altered to be. At the time I was reading a lot of Heinlein, Pohl, and Poul.