I was bound to like this book, really. I've always been engaged with concerns of scientific overreach and the dark side of ambition. That said, I don't usually like a book with such a clear message to convey. But Shelley did a fine job making this into a real page-turner. It's not that the outcome is such a mystery, I suppose. But it's well written, and the arcs of the characters themselves are enough to propel it forward. There are some dry spots with a bit more exposition than necessary (Frankenstein's chronicle of his developing interest in science, for example, or the monster's recounting of his time at the DeLacey cottage), but even these were largely mitigated by Shelley's skillful writing. I have to note, also, that this is the best use of the bookend device I've probably ever seen. Perhaps that's because it's not truly a bookend—Walton actually enters Frankenstein's story before it's finished, and he becomes a significant factor in its completion. Or perhaps it's because of the way our narrator's ambition parallels Frankenstein's own. But it works nicely here, and ties the story up perfectly at the end.
The greatest testament to the novel's genius is probably that, almost two centuries later, it's at least as thought-provoking and relevant as it could have been when it was written.