I do not regularly read the Septuagint, but there are times when a passage from it is helpful for work in the New Testament. At such times the last thing one wants is to encounter an unfamiliar vocable or a vocable that has a twist in meaning different from the usual New Testament meaning. Such words are not likely to be found in other Greek lexicons. For such times this work is very helpful. It is not exactly a concordance to the Septuagint, but does give several passages where the word is used, sometimes indicating the list is complete for all occurences. It is spendy, but a very good resource. Put it on a wish list and wait for someone to buy it for you.