Just as Mark Smith posted earlier I have just acquired a free Vyrso book.
I have automatic downloads set to No so was prompted to approve it which I did. It downloaded and started indexing in the background which was nice.
I had the indications below

But I checked a little later and it had

which was somewhat surprising!
Shortly after the indexing icon disappeared altogether
Note there were two indexing operations taking place. The first for the Greek Grammatical Constructions Documentation and the second for the Vyrso book "Thou Shall". My description above relates to the second operation