In 1910 there were 175,000 Jews in Vienna, a number exceeded in Europe only in Warsaw and Budapest. Vienna was also the European city where the number of Jews converting to Christianity or to no religion was greatest. Between 1868 and 1914 about half those leaving the Jewish community became Catholics, a third became Protestants, and a sixth became konfessionslos. Todd Endelman, in his authoritative collective volume Jewish apostasy in the modern world (1977), states (p. 84) that most of those German or English Jews who converted in that period ‘ceased being nominal Jews and became nominal Christians instead. Their reasons for changing religious allegiance were secular and opportunistic’. Astrid Schweighofer aims to challenge, or at least nuance, this widely accepted judgement. She is especially interested in the question of why so many of those leaving the Jewish community chose to join the relatively small Protestant Churches, rather than the Catholic Church to which some 80 per cent of the city's population belonged. She looks for ‘factors in’ rather than ‘motives for’ conversion, arguing that these were complex and many-sided. Her innovation is to make intensive use of diaries, letters and the archives of the city's Protestant congregations. The most important factor influencing the large numbers of conversions seems to have been marriage. Austrian law did not allow the marriage of a Jew to a Christian, so when such a marriage was contemplated one of the partners had to convert. But many other factors played a part. Schweighofer agrees that most of the converts came from families that were largely or entirely non-observant. Indeed she stresses distance from the Jewish community and rejection of Jewish religion as a major reason for seeking alternatives. She also gives due weight to escape from the antisemitism that was politically powerful in Vienna at the time; to career; to the influence of friends and relatives who had already converted, as well as, in the case of Jews belonging to the professional class, social contacts with bourgeois Christians. But why Protestantism? One reason was that Protestantism was seen as the authentically German religion, and that many of the converts had a strongly German identity. Their papers are full of references to Kant, Goethe, Beethoven and Wagner, and sometimes to a political as well as cultural nationalism. The most important aspect of her book is that Schweighofer places these conversions in the context of the religious ferment of the years around 1900. Some, indeed, like the Social Democratic leader, Victor Adler, had rejected Judaism and chose Protestantism as the least bad alternative, since Austrians citizens were required either to have a Konfession of some kind or to formally declare themselves konfessionslos, a status he regarded as carrying social disadvantages. However, many were ‘seekers’, attracted by the liberal ethos (both theologically and politically) of the Protestant Churches (in practice, usually the Lutheran Church, as relatively few chose the Reformed). Many were attracted by the figure of Jesus, whether or not they saw him as the Son of God. But the religious search of this time also went in many less conventional directions, including Theosophy and an individualised mysticism of a kind often associated with the 1960s. The 1960s were in some respects part of the ‘long 1890s’ – as Schweighofer comments (p. 207), ‘the longing for a religious orientation, within, on the margins, or outside institutional religions and confessions, led to an enormous extension of the religious landscape’. She provides some fascinating family histories, noting that while some parents were deeply distressed by their children's conversion, others positively encouraged it. The latter was the case with the philologist, Theodore Gomperz, all three of whose children converted in the early twentieth century: the philosopher, Heinrich, was interested in religion but personally agnostic; the artist and writer, Bettina, was a mystic; and the engineer Rudolf (who, like a number of the figures discussed in the book, was ultimately murdered by the Nazis) was an orthodox believer. Schweighofer conclusively establishes the important of religious factors in at least some of the conversions in these years, though of course the dependence on surviving personal documents means that the focus is on a small elite group. Although she dismisses the role of missions to the Jews, their impact, if any, was probably on a different section of society. She makes her point partly by tracing the individual journeys of some of the most interesting individuals, including Arnold Schönberg, who ultimately reconverted to Judaism; the philosopher Edmund Husserl, who was strongly influenced by Protestant theologians while studying in Germany; the Richter sisters, both writers, who regularly attended Protestant services long before they formally converted; and the writer Otto Weininger, who was an extreme example of a convert from Judaism who in his brief later career (he killed himself at the age of twenty-three) denigrated all things Jewish. This is a well-researched and impressively thorough study. It is in some ways too thorough in that the important and convincing central argument is supplemented by many interesting, yet not always important details, as well as lengthy quotations from primary sources.