In this verse exactly the Arabic word of Imam is used. but amazingly it is translated "register".
It will be interesting to know why the Arabic word امام (Imam) is translated to register or book.
Anyway this verse is clearly saying "clear Imam"
إِنَّا نَحْنُ نُحْيِي الْمَوْتَى وَنَكْتُبُ مَا قَدَّمُوا وَآثَارَهُمْ وَكُلَّ شَيْءٍ أَحْصَيْنَاهُ فِي إِمَامٍ مُّبِينٍ
Indeed, it is We who bring the dead to life and record what they have put forth and what they left behind, and all things We have enumerated in a clear register. http://tanzil.net/#36:12
The question is who is this Imam in this verse?
Please avoid any answer or tafseer without evidence from Quran or hadith. even if it is the commentary (personal idea) of a famous interpreter of Quran but without any hadith as evidence.