I was so exhausted that I didn't want to study, let alone even think.
Literal
Completely-tired [because-ので] study [nominalizer-の] [topic-は] of-course think [nominalizer-の] [also-も] disliked.
疲れきっていた uses 切る as an auxiliary meaning 'completely, thoroughly.' もちろん...も means 'of course...too / let alone.' The sentence escalates from studying to even thinking — a vivid expression of total exhaustion.