He should 've burned the books.

Heinous, sickening, morally wrong on almost every accountable level, yes, but he should have burned them. If he had, there would be no pile of soil on Mike 's land, no sword pressed up against Erwin 's thigh. It would have been an inelegant solution to an inelegant problem: Jansen would ask,

where are the books,

and Erwin would say, truthfully ' there are no books. There is not a single thing for you to hold over my head, Commander. And Jansen could threaten, but the truth would be clear, after a time, and he would have nothing to use against Erwin except the knowledge of his love for his subordinate, and Levi is not someone you catch off-guard twice.