The book makes three main interventions. First is the use of Jewish economic history to understand both the development of Jewish society and its relations with the surrounding world. The methodology of New institutional economics, emphasizing the connection between economic and cultural factors, is employed. Second is the study of the Jews' economic roles in the specific context of magnate estates in eighteenth-century Poland-Lithuania. In this late feudal setting, Jews achieved enormous financial success, which they translated into improved social status and even power. This process is at the heart of the analysis here. Third is the history of the Radziwiłł family and its estates in Lithuania. From a low point at the beginning of the period, the family reached the pinnacle of its power at the end. This rise was based on increased estate incomes, the importance for which of Jewish economic activity is examined here.

Jewish settlement on the Radziwiłł estates in Lithuania grew rapidly from the end of the seventeenth century. The Great Northern War of 1702-1720 did not hit Jewish settlement particularly seriously and may even have encouraged its growth in the period of reconstruction. By 1764, the Jewish population on the family's Lithuanian estates had reached some 20,000—almost 10 percent of the total Jewish population in the Grand Duchy. The dominant form of Jewish settlement was communities in the small agricultural towns, where they made up a large proportion of the population. Finally, by examining the Radziwiłłs' legislation on the issue of Jewish settlement and comparing Radiziwiłł-run estates with others not administered by the family, it becomes evident that Jewish settlement grew and developed as a direct consequence of a conscious policy adopted by the Radziwiłłs and their administration.

Towns were the main setting of Jewish life on the estates, with Jews there contributing greatly to the urban economy and bringing significant revenues to the Radziwiłł administration. The Jews' importance in the economies of both large and small towns was felt most in their domination of trade, and in particular alcohol sales. In terms of direct taxation, individual Jews seem to have paid proportionately less than non-Jews. However, both individual Jews and communities were called on to make extensive unofficial contributions, while communities also made extra payments, such as those for rabbinic licenses. Both the community councils and the rabbis acted as unofficial agents of the administration, responsible for managing the Jewish population and its economic activity. Despite this, wealthy Jews who served the Radziwiłłs directly could exempt themselves from communal jurisdiction, creating a new socioeconomic elite.

The raison d'etre of the estate system was providing the Radziwiłłs with revenue from agricultural activity. There were four main strategies for doing so. The first was direct administration: the family established a complex administrative system, which gave it extensive, though never complete, control over estate management. For immediate income, it could choose to mortgage an estate, making the lender legal owner until the debt was repaid. In case of default, he retained the lands. Another option was giving an estate on leasehold. The lender would receive control, not ownership, of the lands for the term of the lease; estate incomes formed repayment and interest. The fourth strategy: leasing out the incomes from the estate owner's monopolies—most importantly, the manufacture and sale of alcohol. This was the only field in which Jews were deeply engaged in this period. Its profitability made it the growth sector of the estate economy.

The career of the brothers, Szmojło and Gdal Ickowicz, who leased the Radziwiłł holdings from 1740 to 1745, exemplifies the possibilities and risks of estate leasing for Jews. Their success was based on their entrepreneurial skills in using leases to improve their trading activity, and mercantile profits to expand their leaseholds. Their willingness to change the economic status quo by unilaterally increasing customary dues allowed them to improve estate profitability, boosting Hieronim Florian Radziwiłł's revenues. They thus won his confidence, with Szmojło becoming his personal agent. Their highhandedness made the brothers extremely unpopular. A peasant uprising ensued, during which Radziwiłł supported them. For as long as they could provide him with increased revenues, they flourished. Once they could not, they were at his mercy. When he needed income that Szmojło could not find, Radziwiłł arrested him, confiscated his fortune, and left him to die in prison.

It was leases (arendas) on various incomes from monopoly rights that kept estate revenues rising. Alcohol sales were a particularly important way of selling grain on the home market. Prices rose, boosting profits, and leading Radziwiłł to expand the number of leases by investing in tavern building. He also instituted "general arendas" that included all the incomes on a single estate, allowing the wealthy Jewish leaseholders that took them to work alongside his administration as unofficial managers of monopoly incomes. Radziwiłł also used these leaseholders as personal bankers, disbursing money through payment orders drawn on them. The leaseholders gave the separate parts of their leases to less wealthy Jews, who ran individual taverns. To keep revenues up, the administration supported its leaseholders against non-Jewish clients who avoided paying their dues. The Jewish leaseholders thus formed a powerful group in estate society, clearly identified with the Radziwiłł administration.

Jewish merchants were, with Radziwiłł encouragement, the dominant force in local markets. They were particularly important in allowing the estate administration to take advantage of new opportunities in the eighteenth century, which its established systems were unable to do. Trade served the estate economy in three ways: distribution, supply, and revenue generation. The arendarze boosted grain sales in the new economic conditions and Jewish merchants enabled the family to penetrate the new export market in flax and hemp. Jews were extremely important in supplying estate society. This mercantile activity also generated huge revenues in the form of indirect taxation. The importance of Jews in revenue generation is seen in the family's expanding river trade to Königsberg starting in the 1720s. The freight payments Jewish merchants made to ship their goods on family rafts made this newly flourishing trade viable for the Radziwiłłs, giving them easy access to the international market.

The Radziwiłł administration's economic policy provided the framework for the Jews' success. They identified and played key roles in the estate economy by seizing the new opportunities of the eighteenth century. This allowed them to both serve Radziwiłł interests and create an ethnically dominated economic niche in trade and arenda. This proved so important to the estate economy that the administration gave them strong support. They thus increased their market domination, and, by becoming identified with the Radziwiłł administration, amassed power and authority in estate society. This power was, however, contingent on providing the services the administration wanted. The Jews' success in boosting estate revenues helped the Radziwiłłs, like similar magnate families, become the most powerful force in Poland-Lithuania. Jewish economic activity was thus a key factor in the development of the Polish-Lithuanian Commonwealth in the eighteenth century.