Mailer's endless epistolary

Just a moment ago, I was about to take a picture of the cover of the book I finished reading a couple of days ago.  I thought about angling back to get a sense of the size of this thing before deciding it just wasn't worth it.  The novel that I just finished is Norman Mailer's Harlot's Ghost.  This is a giant novel about the CIA and spies, the Kennedys and Cuba, the Bay of Pigs, and a bunch of uninteresting personal relationships.  There are long epistolary sections that detail a love triangle involving the principal character, his mentor, and his mentor's wife.
Most of the action is mediated through either letters or through transcripts of dialogue that is caught  between other characters.  This creates a narrative distance from the events of the novel that makes it difficult to engage with the actual story.  Much of the novel depends on the reader's interest in JFK and the imagined romance that Mailer creates for him with a stewardess.  The novel does what movies like some biopics do, which is to intimate a secret, insider knowledge of a historical figure by inventing parts of his life.  This book does not pretend to represent historical accuracy, so the intrigue seems empty and more prurient than actually intriguing.
As I sit here thinking about this, the novel reminds me of Don DeLillo's Libra, which covers some of the same territory but delves into Lee Harvey Oswald's life instead.  DeLillo uses a more immediate form of story telling to investigate Oswald's guilt and intentions, which ends up being a lot more interesting.
The biggest thing missing from this very large book is a return to the inciting incident.  The novel opens with the main character married to his lover and mourning the loss of his mentor, the eponymous Harlot.  Living in Harlot's family mansion, the main character is questioned by a fellow CIA operative who has broken into the home in the middle of the night ahead of a larger team of investigators.  This sets of his story about his past and growing up in the CIA.  The story never comes back around to how the characters got together, or how they came to live in Harlot's home.  The end of the novel, after 1,200 pages, notes that the story is to be continued.  Presumably, some of these strands will be continued as well.  The drive to finish this novel does not extend to reading another monster, so I guess I will never know what became of Harlot's buddies.