Am I rewarded for reading a book of Quranic exegesis (tafsir) as much as I am rewarded for reading the Quran itself?

Reading the commentary (tafsir) of the Quran is a great good for contemplation and acting upon it. Allah Almighty commanded His Prophet, peace and blessings be upon him, to explain the Quran to the people. However, there is no evidence that the reward for reading tafsir is the same as the reward for reading the Quran. Regarding reading the Quran, it has been stated that for every letter there are ten good deeds, and that it will intercede for its companions on the Day of Judgment, whereas no specific reward has been mentioned for reading tafsir that would equate it with the reward of reciting the Quran.