I'm not sure what you're asking. Do you mean the Tangut kingdom Xi Xia? There is some substantial coverage in F. W. Mote, Imperial China 800-1900 (Harvard University Press, 2000). There is also a chapter about Xi Xia (spelled Hsi Hsia) in the Cambridge History of China, volume 6.

If you mean the Tangut language, a book has just come out: Jinbo Shi, Tangut Language and Manuscripts: An Introduction (Brill, 2020).

For the early Tangut kingdom, there's Ruth W. Dunnell's The Great State of White and High: Buddhism and State Formation in Eleventh-Century Xia.