The main purpose of the novel is to entertain, this one doesn't. The chain of events -or no events- is somehow boring. The intersection between telling events, conversations, details of characters is excessive, making the reader always alienated from the plot and somehow not capable of sharing any kind of emotion with the characters.
Yes, I know more about Lisbon now than before. I understand a bit better how people were living and thinking in the 30's in Portugal (and somehow in Spain). But many other authors presented their societies, cities and ideas in a way better book (Doris Lessing in The Golden Notebook about London in the 50's and Jonathan Franzen in Freedom about the NY and the US in the 90's for example).
The book in general worth reading, the style is good if not great and Saramgo is a novelist who deserve Nobel for sure, but this is not his best book and if it happen to be your first for him, you would definitely put him out of your list.