We get two whole sentences into The House of Spirits before we're hit with the theme of reclaiming the past. And, in a sort of beautiful symmetry that we literature nerds get super excited about, the second-to-last sentence hits us with it again. The idea of using the past to better understand the present and to prepare for a future is a theme of this novel, and it's bound up in the idea of storytelling and writing, since those are methods that the characters use to preserve memory. Check out the section on "Literature and Writing" to see how the two themes connect.
Clara and Alba are arguably the two most central characters in the novel, thanks to their role as family scribe – they are the recorders and keepers of memory for the Trueba family.
In The House of the Spirits, people have different recollections of the same events, and those recollections may change over time. Memory therefore isn't presented as something solid and unchangeable – Truth with a capital "T" – but rather as a product of the desires and imaginations of the characters.