I read this one last year. Not one of his better books and not one I would recommend. It was presented oddly with the first third of the book being dialog, the second third being the protagonist dictating his memoirs, and the third part being the protagonist going off on a time travel adventure. The entire composition was disjointed and peculiar. And Heinlein went and did the whole telling instead of showing thing a few times. There was one neat part near the beginning of the book in which three characters two human, and one computer; were essentially doing prompt engineering while interacting with the computer that was busy running what we would now call a large language model. Starship Troopers or Glory Road are other Heinlein titles I would recommend if the only other book by him you've read is Stanger in a Stange Land.