As children's/almost young adult books, they're fun. They tend to deal with real issues, but in an accessible way. In this case, two twins who are very different, but struggle against that. They're also dealing with the death of their mother and the new relationship of their father. These are all real issues. (The other one I read was about a girl in fostercare.) But for all that, they're fairly light, very fast reads, and while I wouldn't worry about kids reading them, they're not really deep.
But Ruby and Garnet are appealing. Ruby wants them to be actresses, but Garnet is terrified of getting up in front of people. Ruby hates their new life and new school, but Garnet starts to make friends. Ruby takes the lead, Garnet follows, even if she disagrees. And Ruby is so headstrong she tries to drag them into being actresses, without ever listening to her sister.
The characters are lightly drawn, but nicely complex. Their dad's new girlfriend is both exasperated and understanding. Their beloved grandmother is also a little nitpicky. Their dad is trying hard, but coming apart a bit at the seams. Nobody in this book is a monster, even the town bully.
And the twins eventually learn that maybe doing things apart isn't as bad as they thought. It's a good light read for children, but I don't know how long it would stay with them. When I think back on the books from my own childhood that have stayed with me, they're the ones that are more complex, that challenged me with ideas and adventures beyond the commonplace. I guess I never much cared for straight-up fiction as a child. That came much later.
Read as part of the BBC Big Read