Heard over Shabbos an interesting question on the Rambam's formulation of the mitzvah of a king to write a second sefer Torah. The gemara (Sanhedrin 21b) implies that both the sefer of each individual as well as the sefer of a king must be written by them and not inherited from a parent. The Rambam is clear in hilchos sefer Torah that each individual must write his own sefer and not merely inherit one. Yet, when it comes to the king, the Rambam writes (Melachim 3:1) that the mitzvah is to write a sefer "in addition to the sefer left [to the king] by his father...If his father did not leave a sefer or it was lost, the king must write two toros". What does the Rambam mean by the words "in addition to the Torah left by his father" - the king is obviously not yotzei his mitzvah to write his own individual sefer with the sefer inherited from his father, and is not yotzei writing a second sefer either through inheriting one?! The Kesefe Mishne as well as Minchas Chinuch raise the issue - M.C. offers no answer; KS"M rereads the whole gemara b'dochak.
While on the topic, the Rashash sometimes throws a radical curveball at you, and this mitzvah is one of those places. He writes (Sanhedrin 21) that the king could not shlep around a full sefer Torah with him. This second sefer was no more than an abridged version listing the 613 mitzvos. You definitely do not get this impression from any of the rishonim!