What is the extant evidence for what Shang society was like? Is it the Shiji plus archaeological artefacts, basically? What sort of material do we have in oracle bone script?
The oracle bone findings from Anyang are the primary source of information on the Shang dynasty. Because they were communications to deity, they cover a wide range of topics from harvesting crops to human sacrificial instructions and contain thousands of characters. [1]
Virtually every work on the Shang dynasty references the oracle bones. Of course, the additional archeological artifacts and sites are vital for information, like the mass tomb in Anyang I mentioned in the other question about sacrifice.
As far as using the Shiji and other Han-period works, I'll defer to Gideon Shelach, professor of East Asian studies and archeologist specializing in Neolithic and Bronze Age of north China:
"The problem common to all these primary sources is that they were written during the latter part of the Eastern Zhou (771-221 B.C.) and the Han (206 B.C.-A.D. 220) periods. Although these later sources may rely in part on older documents, knowledge of some aspects of the Shang period was lost during a thousand years of oral transmission ... Further, the historical texts reflect a view of non-Han people as inferior to the Han. This means that descriptions regarding non-Shang people are even less reliable than the other contents of these documents."
The oracle bones are a fantastic resource and look into a bronze-age culture. They're similar to cuneiform or hieroglyphs in the sheer number of existing pieces and information.
Thanks for exploring the question further; I hope that helps!
[1] Qiu, Xigui (2000). Chinese writing (Wenzixue gaiyao). Transl. by Gilbert L. Mattos and Jerry Norman. Berkeley: Society for the Study of Early China.
[2] Shelach, Gideon. (1996). The Qiang and the Question of Human Sacrifice in the Late Shang Period. Asian Perspectives. Vol. 35, No. 1.