Who was Yitzchaki?
In his commentary on Beresheet 36:31, Ibn Ezra writes:
"ואלה המלכים. יש אומרים כי בדרך נבואה נכתבה זאת הפרשה. ויצחקי אמר בספרו כי בימי יהושפט נכתבה זאת הפרשה. ופי' הדורות כרצונו הכי קרא שמו יצחק כל השומע יצחק לו. כי אמר כי הדד הוא הדד האדומי ואמר כי מהיטבאל אחות תחפנחם. וחלילה חלילה שהדבר כמו שדבר על ימי יהושפט וספרו ראוי להשרף ולמה תמה על שמנה מלכים שמלכו שהם רבים. וכו'"
"And these are the kings. Some say that by way of prophecy this section was written. And Yitzchaki said in his book that in the time of Yehoshaphat this section was written. And he commentated the generations according to his will, and because of this he was named Yitzchak, all who hear laugh at him. For he said that Hadad is Hadad the Edomite and that Meheitavel the sister of Tachpanches. And God forbid twice that this would be as he said about the days of Yehoshaphat, and his book is deserving of being burned and why did he wonder that he counted many kings that ruled etc"
Who was this Yitzchaki person that deserved to have his book burned? He appears to have been, at the time, some sort of well-known heretic. In the book Ezra L'havin, it says he was a Karaite. Is there any more information on him and his book?