Along with the new Avotaynu Guide, indispensable.
Kurzweil's book is not as lengthy and technical as the Avotaynu book, nor as concise and tightly organized as Barbara Krasner-Khait's Discovering Your Jewish Ancestors (2001). But what it offers is something unheard of in genealogy textbooks - a work that reads like a novel. He is not afraid to be expansive and anecdotal, even chatty. His personal stories with genealogy, dating back to 1970, are gripping. Especially so because Kurzweil (unlike many genealogical authors) knows how to tell a story. The book is often lyrical and intensely earnest, without being melodramatic or overwrought. His passion for discovering his ancestral roots is sincere and infectious. In fact, his discovery of a descent from a famous Hasidic rabbi led him to embrace more traditional Judaism in his spiritual life.
But the book is not ALL personal stories, as interesting as they are. He packs the bulk of these into his opening chapters, and then sprinkles them as useful illustrations throughout the work. He covers all of the important topics, and is quite up to date on the online resources (through about late 2003). He has a great command of the details of doing Jewish genealogy, and he has some very brilliant recommendations for some unique and creative sources. (He was a founding father of Jewish genealogy in the mid-70s, and has given something like 600 lectures around the country).
His enthusiasm is infectious, and he makes strong arguments for the moral and spiritual value for Jews to explore their roots (bolstering his case with short gripping quotes from the Old Testament, Jewish sages, and Talmud). Further, he makes a good case against cremation (with which this Christian reviewer agrees).
The only shortcomings of the book:
1. As noted above, this is not absolutely comprehensive. You will want both the Avotaynu and the Krasner-Khait books to fill in all of the blanks.
2. While a good scholar and critically oriented, he is generally a littel more eager than I am to accept oral traditions or unproven claims of rabbinic lines. See, for example, the material pp.30-34. At the end he is willing to claim it is `likely' he is a direct descendant from King David, because a certain famous rabbi living 1500 years after David claimed descent from him (how could he know?). And another rabbi living 600 years later claims to be a descendant of that rabbi, etc. Four or five jumps like that and Kurzweil makes it to his famous 3x-great-grandfather rabbi. Utterly unprovable beyond perhaps the first or second `jump' backwards, and pretty unlikely. But in fairness, he acknowledges the problems with these rabbinic genealogies.
In any case, a wonderful read, and a good practical tool.
It might make a nice gift for a relative who is mildly interested in their family history, but in need of inspiration to get more involved. Also, every synagogue library, public library, and local historical society needs to have a donated copy (along with the Avotaynu guide). And at just $16 (for a beefy, nicely illustrated hardback), VERY affordable.