I couldn't decide whether
The Magician's Nephew deserved 2 or 2.5 stars, but since there's no half-star option on Goodreads, 2 it is.
I don't think
The Magician's Nephew is a wholly convincing start to the Narnia saga. Sure, there's the requisite continuity (where they bury the rings) and character backstory, but the story feels dead.
Now I quite enjoyed seeing Jadis' 'origin' (in scare quotes because we still have no clue how she arrived in Charn, or what sort of things she had done there) and there were some funny moments. But overall I was not interested in reading about Aslan singing or some cab driver getting pulled into a new world. The most interesting idea was the rings themselves; however, they create a sort of infinite regress:
Narnia <= rings <= ? </blockquote>
In other words, where did the rings come from? This is akin to creative panspermia, the (silly) origin of life idea that postulates aliens landing on Earth and creating life. Well, where did the aliens come from? Similarly, where did Aslan come from? Where did Charn or the jumping-point woods come from?
The Magician's Nephew is not so much a story as it is a religious metaphor. Since the questions raised above don't have any simple narrative answers (barring "the author wrote it that way"), they become more philosophical and indeed religious in nature. If that's what you want to read, by all means go for it! But if you don't like religion in your fiction, this may not be the best choice.
My ambivalence toward Nephew doesn't result because the questions are religious in nature but because the questions are there at all. I like a nice, neat story that plays by the rules of reality. This is one origin story that seems a bit too far-fetched for my tastes.