First of all, I am reviewing this book based on the English translation of it. The language is smooth and beautiful.
Secondly, I have read Paulo Coelho's more famous work, The Alchemist, and am not a fan - it feels too heavily symbolic and spiritual to be an engaging read for me.

The Witch of Portobello chronicles the life of Athena, and is told after her death by various people who knew her. Her mother, her teacher, her employer etc each contribute passages, which are then collected by the fictional biographer and woven into a version of her life and deeds. The structure is a parallel of the Gospels: intentionally so, as Athena is a female Christ-like figure to bring back the female side of god.

And, while reading the novel, it feels like the symbolism and spiritualism, the themes and parallels within are being hammered into you.

There's the idea of self: what is a self really? All the perceptions of Athena seem to differ.
There's the idea of the female side of god, of the mother's role in spirituality.
There's the idea of the established religion smothering all alternatives.

Interesting ideas, yes, but the ideas feel more alive than the characters within.

And as for the story, part of the problem is that there is such a build-up on Athena's character in the first half of the novel (characters saying, What, what did she do?!), that the end felt too weak to justify the suspense. But anyhow, the plot doesn't feel like the main point of the book. It is just another way to express a parallel to Christ.