This is really two stories in one. It's the story of a teenage girl after she's saved the world from her evil witch mother, and it's the story of a sci-fi fan.
The evil witch angle first: There's magic, but it's highly deniable - when the magic's done, there's always some other excuse for what happened, possibly stretching back in time before the magic was done. The protagonist managed to stop their mother using magic to become very powerful, getting injured and losing her twin sister in the process.
The sci-fi fan angle: The protagonist reads lots of sci-fi and fantasy. It gets her through the bad times as she's left her mother, meets her estranged father, and is sent to a strange boarding school far from anything she's known. She goes on about how great libraries and inter-library loans are.
I'm not selling it well, but it's a pretty enjoyable story. The magic part was rather more interesting to me than "sci-fi and libraries are great if you're an isolated teenager in the late '70s". On the other hand, if you took out the constant wittering about sci-fi, the book would fall apart.
It received plenty of decent reviews, but I think it got a heap of praise on Boing Boing because of the "Oooh, books and libraries" angle. The more I look at that part, the more it leaves me cold. Partly because I don't care for '70s-or-earlier sci-fi. Partly because I find effusive praise from Ursula Le Guin on the cover less interesting when the heroine is praising Le Guin in the body of the text. Partly because "libraries are great (in the '70s)" feels like the thinnest cover-up for "they shouldn't close libraries".
Libraries are a wonderful idea. However, the idea we should be keeping libraries at the same scale as in the past, at least in that form, is some kind of weird non-sensical nostalgia thing. In the '70s we didn't have the internet. Not everyone had access to wikipedia. To vast numbers of scientific papers, if they want them. To free access to tonnes of out-of-copyright material, and Amazon supplying pretty much any book you want, delivered in a day or two. To illegal, free access to most any book. Or video, or music.
Growing up, provincial libraries were naff. The selection was eclectic and generally rubbish. Inter-library loans were painfully slow. As a researcher, copyright libraries were amazing, but utterly horrific and tedious to use. I was so glad that most papers I cared about were online. Libraries weren't a sign of the golden age of information, they were a sticking plaster over information poverty.
(Further random aside: I see the traditional role of "librarian" as similarly endangered. A librarian makes sense when full-text search is impossible and the indexing is sparse. It horrifies me conceptually, but the future of information is a big, unorganised mess, and computers combing the rubbish for you. i.e. It's like the web.)
There's still information inequality that goes with social inequality. Getting cheap internet to as many people as possible, and giving those people the tools to use it is the way forward, not an outdated form of libraries. Libraries can fit into that, but not in their traditional form, and clinging to them may be wasting money better spent in other ways to the same end.
I am not impressed by this nostalgia.