This is a difficult book to judge; parts of it verge on the brilliant, parts of it seem unnecessary. In addition, there is always the lurking fear that the translation itself is a significant factor.
In places Marias has superb control, a great depth of observation, and some important and thought-provoking things to say. In particular, his musings on marriage and how two individuals accommodate each other, resonate with the reader. In these places, the characters seem to flesh out and become real and vibrant.
In other places, the book appears to drift. The narrative becomes elliptical, slipping through several eras and time zones within the same sentence. In many ways, it is a confusing book to read; sentences can last 200 words, paragraphs two or three pages. The density this brings might be seen to be fitting to the microscopic detail that concerns Marias. On the other hand, it robs those details of their power - they are caught up in a seemingly endless spool of words, and so remain hidden when they should be standing out. It is difficult to say whether this is the translation, or how it was originally written.
Ultimately, this book is enjoyable because the writer is clearly talented, eloquent and erudite; it is enjoyable because it has some interesting things to say about love and relationships. However, it would have been so much better had it been better structured on the page.