You should avoid citing a source you have not consulted. If you can consult the original source in which the quotation appeared, then you should do that. If you cannot consult the original source, you should cite the source where you found the quotation. When you are citing a quotation that was quoted in someone else’s book, you should indicate this in the following way:
Author Amy Bloom described her husband’s early symptoms of Alzheimer’s as “names disappearing, repetition, information turned upside down, appointments and medications scrambled” (qtd. in Van Booy).