Caddy's World. This book is actually a prequel to the series, but I would recommend reading them in publication order, as this book gives away (or at least strongly hints at) one of the major plot points from Saffy's Angel.
Before Darling Michael, before the hamsters, even before Permanent Rose, there were four friends -- Alison, who hates everyone; Ruby, the clever one; Beth, who is perfect; and Cadmium Gold Casson, bravest of the brave. "You four will be friends," their first primary school teacher instructed . . . and so they were. But now, during Caddy's twelfth summer, her beautiful, unchanging friendship seems to be coming apart. Alison's parents are threatening to sell their house and move their family to Tasmania. Ruby has been offered the chance at a scholarship to a private school. Beth is growing too big for her beloved pony, and Caddy's family is in even more of an uproar than usual because Eve is at the hospital with the new baby, which seems so small that Caddy can't see how it could possibly survive. Will the four friends be torn apart by circumstances, or can they make it through together?
I love the Cassons, and Caddy has always been the most distant one, since she is nearly grown up in the other books. It's lovely to get to know her better here. I don't know if there will be more books in the series (Caddy and Rose have had two books each; I think Saffy and Indigo need more books now), but the epilogue in Caddy's World made me want to pick up Saffy's Angel again and reread the rest of the series.
(Reviewed from a copy borrowed through my library system.)