It's always interesting to discuss the point of view in regards to House of the Spirits! The majority of the narration is truly third person omniscient (called thus because this narrator knows everything and tells the reader). This narrator is always using the terms he or she to refer to people (which is the reason why "third person" is in its description) and always relates what they think and feel.
However, there are a couple of other narrators that are really important to mention. The first time a character speaks in the first person (in other words, using the pronoun I) the reader will realize that the character remains unnamed; however, it becomes clear by the end of the novel that this unnamed first person narrator is Alba herself. There is also another elusive first person narrator in this story: Esteban Trueba. The main reason for the introduction of this new point of view is to voice the character's great pain or anger that he doesn't express in front of others. Without this insight, the reader would certainly misjudge Esteban. The other reason for Esteban's voice is to reiterate the idea that this is a collection of ideas from written and oral family history.
The narrator of House of Spirits is Alba, and occasionally Esteban and several other characters. Alba is essentially the main character because she is not present in the first couple of generations -- making very neutral remarks. However, the narrator sometimes shifts to other character to give the reader an insight of the character's characteristics.