Books here could be a stand-in for what Thomas Kuhn has called paradigms [1]. Broadly, each science has a core set of beliefs that are accepted by a majority of the scientists working within that discipline. Books can be seen as the formalization of a paradigm as a way to teach new people (e.g., undergraduates) how to operate within a discipline as opposed to research papers where the boundaries of current paradigms are tested and pushed (or opening up the black box, as you mention).

[1]: https://en.wikipedia.org/wiki/Paradigm_shift