What is the current state of the law on brief perusal of the contents of a book?

We do not mean to suggest that agents entitled to examine a book or similar item may minutely scrutinize its contents, especially when personal, nonbusiness papers are involved. See Crouch v. United States, 454 U.S. 952, 955-56, 102 S.Ct. 491, 492-93, 70 L.Ed.2d 259 (1981) (White, J., dissenting from denial of certiorari). But this case does not require us to explore the limits to brief perusal. The trial court's factual findings establish that no more than a glance was necessary to ascertain the incriminating nature of the notations.