Edit: I'd recommend reading this book after The Siren Depths but before the last two novels in the series. Actually, I'd also recommend reading after Siren and after the second story collection book. It emotionally sets up the last two novels, which are really two parts of one last book.

I liked the two longer pieces. They add flavor to the series. One was like a side story but showed how their bonding increased between the books. The second filled out some important history.

There were also a couple short stories that were like decoration.