I've read the ten Amber books by Roger Zelazny all the way through ten times, which sorta-counts. A total read-through of those books can be done in a 3-day weekend if you read the whole day, so if you want a rough idea of the time commitment of a centireading, it's about a month of day-long readings. Another way to view it is a task of reading two books a week for a year.

Like the Zelazny books, you need to have something which has the right "flow" for you to really make it work.

My English professor at Cornell was fond of saying, "There is no good writing, only good rewriting. There is no good reading, only good rereading." He calls to mind how it's easier and more powerful to condense and re-articulate your article/book when you know where it starts, where it ends, and how it gets from A to B: then he comments, so too you get a greater appreciation of the details of what you're reading when you can see the overall story.

In the case of the Roger Zelazny books, there was one section in particular where this happened. We see a flashback from Merlin's perspective to a time when he is a teenager and he takes his all-to-human girlfriend on an insane journey through impossible landscapes which putatively exist just-next-door. In the discussion that follows, it seems like, by not telling her his secret, he's shutting her out:

What could I say? It was not only that telling her of Shadow would disturb,
perhaps destroy, her view of reality. At the heart of my problem lay the
realization that it would also require telling her how I knew this, which would
mean telling her who I am, where I am from, what I am--and I was afraid to give
her this knowledge. I told myself that it would end our relationship as surely as
telling her nothing would; and if it must end either way, I would rather we parted
without her possessing this knowledge. Later, much later, I was to see this for
the rationalization it was; my real reason for denying her the answers she desired
was that I was not ready to trust her, or anyone, so close to me as I really am.
Had I known her longer, better--another year, say--I might have answered her. I
don't know. We never used the word "love," though it must have run through her
mind on occasion, as it did through mine. It was, I suppose, that I didn't love
her enough to trust her, and then it was too late. So, "I can't tell you," were
my words.
"You have some power that you will not share."
"Call it that, then."
"I would do whatever you say, promise whatever you want promised."
"There is a reason, Julia."
She is on her feet, arms akimbo. "And you won't even share that."
I shake my head.
"It must be a lonely world you inhabit, magician, if even those who love you
are barred from it."
At that moment it seems she is simply trying her last trick for getting an
answer from me. I screw my resolve yet tighter. "I didn't say that."
"You didn't have to. It is your silence that tells me. If you know the road to
Hell too, why not head that way? Good-bye!"
"Julia. Don't..."
She chooses not to hear me. Still life with flowers...

If you're just reading through this, it seems perhaps like she's gone power-hungry; you sympathize with Merlin. But read through it again. Pay particular attention to that sentence in the first paragraph: we never used the word "love", and then just consider the exchange, "It must be a lonely world you inhabit, magician, if even those who love you are barred from it." / "I didn't say that." On rereading, you realize that from her perspective, she's jumping out into vulnerable territory, using this word which they've never used before, and when he shuts her down, from her perspective he's basically saying "I didn't say that I loved you."