I'm in the humanities and it is normal that after a book comes out book reviews of said book will appear in journals. Now while I think it is expected that scholars write book reviews of other scholars' books, they do it mainly as a service to the field but it doesn't really count for much and are usually are not cited (unless they become part of a larger dispute). Thus they don't really help one's google scholar citation count etc.
Still, they obviously form an important part of the academic environment in the humanities. That is why I was wondering how you use book reviews in your research? I for one, occasionally read reviews of books that I heard of and want to get a quick summary of, but, if I have read a book (say for my lit review etc), I also like to double check whether my interpretation of the book agrees with that of others that have read the book.
Are there any other uses? I suppose I am just wondering because, again, these reviews seem to be quite important (taking up substantial space in journals), but don't get much credit.