This is an insightful look into the sociolinguistic aspects of adults who enter into new communities, in which novices gain expertise in language as well as all manner of other sociocultural aspects. Orthodox Judaism is unique in that there are so many intricacies to be considered that it is not directly comparable to, say, an adult gaining expertise in a new workplace, or even an adult joining religious communities that might have fewer new things to learn. Many of those who come from non-Orthodox backgrounds never fully leave their previous identities behind, perhaps more akin to adult learners of additional languages. (Though there is learning of Hebrew and/or Yiddish in this case, a large part of this book's focus is on Jewish English in particular. The "language and culture" of orthodox Judaism is therefore situated somewhere more intense than the learning of an additional dialect, but perhaps less than the need to entirely absorb news languages in toto.)
This is an invaluable book, and from my experiences in both Judaism and linguistics, its insights ring very true. My only desire might have been to see some larger sample sizes. I don't fault the author, since she documents extensive research over a long period of time, but there are occasions when conclusions might have benefitted from casting a wider net (even if such a net might not have been possible to cast).
All in all, an excellent sociolinguistic resource.