When I've read or heard references to the Kuzari in recent years, I have noticed comparisons of Judah Halevi's Kuzari to the work of Maimonides, contrasting Halevi the antirationalist and Jewish particularist to Maimonides the rationalist universalist. The purpose of this book is to show that there are other ways of understanding the Kuzari, and to create a history of how the Kuzari has been understood over the centuries.
The story begins in 14th-c. Spain and France, where some authors treated the Kuzari not as antirational, but as an attempt to reconcile faith and reason. In Shear's words, some commentators saw the Kuzari "as a necessary prerequisite to the study of Maimonides... or as part of the same tradition."
After the printing press was invented, the Kuzari became more popular in some places, though not in others- most popular in Renaissance Italy, much less popular in Ottoman lands and in Eastern Europe. If I understand him correctly, Shear suggests that 16th and 17th century writers often treated the Kuzari as a kind of general guide to Judaism. And as books got cheaper in the 19th century, Jews of all stripes mined the Kuzari to support their views.