Little, Brown Book Group Certain Magical Index, Vol. 1 (light novel)

In Academy City, magic and science coexist in an unwavering power struggle. Toma Kamijo, an academically-challenged student in Academy City, wields the power of the Imagine Breaker in his right hand, which allows him to completely negate all supernatural powers - as well as his own luck. When he happens upon a mysterious nun named Index, whose mind has been implanted with the Index Librorum Prohibitorum - 103,000 ancient texts banned by the Church - Toma's luck is about to be pushed to its limits when he finds himself in the middle of a war he never expected!