Todd tells us in the acknowledgement that Anne died after they wrote the book and before it was edited. He also says he'll continue in Pern.
All of the books in this group of Pern books are very related to the others, and it helps to read them in the published order. For this, you really need to read the one before it.
They start with not enough dragons for the upcoming Thread, but like other books, have a group of people and dragons move in time and place, and solve the problem.
There's really no reason to get more specific -- if you've read any Pern, this is similar, and if you haven't, this is not the place to start.