What are some examples of books where an important event is not revealed to the reader?

Great Expectations, and the mystery/assumption about Pip’s benefactor.

Speak. It’s more like the event happens in the past, and then the book is the young woman in the aftermath of the event, and how it effects her (but also, how other things effect her).

You may also find some examples here, or on one of the similar tropes listed. But do not click, unless you have time to fall in…

Catch-22 does this with the death of Snowden. It is the event that drives the main character’s actions. It and what you later realize are consequences of it are alluded to in tiny slivers throughout the book, but the actual event isn’t described until quite late in the book.

I’m not sure this exactly fits, but “The Photograph” by Penelope Lively starts when a widower finds a picture of his dead wife and her brother-in-law holding hands. A web of friends and family all remember the her in different ways and their perspectives start to come together to make an incomplete picture. We learn how and why she died at the end of the book, but the author barely tells us anything about the affair itself or why it happened, even though that set off the whole investigation.

“By Chance” by Martin Corrick has an event which drives the plot, but you don’t find out what happened until near the end of the book. At the beginning, a mild-mannered, thoughtful middle-aged man travels to a remote island to live in a boardinghouse full of odd people. The book alternates this with descriptions of his youth and married life, which was innocent, domestic, and insular- they were completely wrapped up in each other and happy that way. At the end of the book, the protagonist tells a new friend about the personal catastrophe that led him to the island and it completely changes the picture, casting a shadow over his life and the island. It’s a great read.

In the sequel to Day of the Triffids, called Night of the Triffids, the book begins with a mysterious black out, causing virtual blindness without a flashlight.
The book winds through numerous plot complications, but never solved the opening mystery.

In Ulysses, by James Joyce, there an instance of a very important event not being disclosed to the reader. In Episode four Leopold Bloom sees a letter for his wife Marion (Molly) in the hall and delivers it to her in the bedroom. The letter is from a concert promoter, Hugh (“Blazes”) Boylan, who is going to revive Molly’s singing career. The reader is aware that Leopold is unhappy; he strongly suspects that Molly will commit adultery with Boylan very soon. The conversation in the bedroom goes like this:
—Who was the letter from? He asked. [...]
—O, Boylan, she said. He’s bringing the programme.
Throughout the day we get an insight into Leopold’s thoughts through Joyce’s use of interior monologue, or Stream of Consciousness. It is clear that he is almost driven to distraction by his wife’s impending unfaithfulness. “At four, she said” crops up in his thoughts in Episode eleven, and it is clear to the reader that this is the appointed hour of Leopold’s cuckolding. On three other occasions “at four” comes into his mind, despite his frantic efforts to divert himself away from it.
Since morning Bloom has being tormented by the fact that Boylan will visit Molly at four o’clock and have sex with her. But here’s the point: how does he know Boylan is coming at four?
It is clear from the context that Molly did reveal to Leopold that Boylan was coming at four. So why is it omitted from the dialogue in the bedroom earlier? The Joycean scholar Hugh Kenner suggested that Bloom returned to the bedroom shortly after the initial dialogue and asked Molly when Boylan would visit. By keeping this information from the reader Joyce was able to convey how Bloom was desperately trying to keep it out of his own mind throughout the day. It was too painful to contemplate, so Joyce had him repress it by omitting the confrontation from the text, and only revealing it to the reader through Bloom’s fleeting flashbacks.

Kate Atkinson has written a series of wonderful mystery **novels using as her protagonist a Scottish Private Investigator named Jackson Brodie.

A unifying thread is the memory Brodie has of his 17-year-old sister being raped and then murdered.

In all four of the novels (so far) Brodie returns again and again to that memory.( He was 12 at the time). It defines his personal and professional decisions, his relationships with the important women in his life and his emotional impulsivity.

So far, there is no resolution, and the author implies that there will be none.

Similiarly, film director Michael Haneke believes that some mysteries do not have to be solved or resolved to make an artistic point…See his brilliant movies, Caché and Das weisse Bande.

**Case Histories; One Good Turn; When Will There Be Good News; Started Early, Took My Dog.

__The Road__ by Cormac McCarthy
It is a post apocalyptic novel of a man and his son on the road scrounging for survival in a very bleak and dangerous landscape. The exact nature of the catastrophic event that caused the destruction is never revealed, only its aftermath.

Rebecca – Daphne du Maurier… The dead ex-wife Rebecca haunts the entire novel, but it is not until very near the end that the full story is revealed…

Not hugely relevant, and not quite in keeping with what you’re asking, but in the book One Day, with just the same date of each year featuring, the main man finds out his mother has cancer on the day after… so we only read about the effects over the following years as the story unfolds and you piece it together in your mind over the course of the next few chapters.

Then, completely not answering your question, the film Memento is shot in reverse, so you only find out what happened at the beginning of the story at the end of the film.

Life of Pi.