This is Neal Stephenson's Seveneves - all quotes here are from the first 35 pages; pages 3-108 are available on Amazon as a free sampler. It made Time's "Top 10 Fiction Books of 2015".
It takes place within our current time frame
The exact start date is not laid out in our year format:
The moon blew up without warning and for no apparent reason. It was
waxing, only one day short of full. The time was 05:03:12 UTC. Later
it would be designated A+0.0.0, or simply Zero.
However, the ISS as described in the book is reasonably close to the level of technology we have today, enough so that it's reasonable to say it happens today. None of the technology described greatly exceeds current (2016) levels.
deals with the Moon getting struck and fragmented into (initially) 7 pieces
In any case, the result was that, first, the moon was fractured into
seven large pieces, as well as innumerable smaller ones.
by a high-speed asteroid that they called "The Agent".
The root cause was unknown - probably not an asteroid; the theory mentioned as leading was a "primordial black hole" passing through at high velocity. But it was called the Agent:
In a sword-fighting drill, where one participant is going to mount an
attack and the other is to respond in some way, the attacker is known
as the agent and the respondent is known as the patient. The agent
acts. The patient is passive. In this case an unknown Agent acted
upon the moon. The moon, along with all the humans living in the
sublunary realm, was the passive recipient of that action.
scientists figure out the the Moon will continue to break down
in a cascade reaction over the next couple of years until the
planet gets bombarded by so much debris that it sterilizes Earth.
"We'll see an increasing number of meteorite impacts. Some will cause
great damage. But overall, life is not going to change that much.
But then" - he clicked again, and the plot bent sharply upward,
turning white - "we are going to witness an event that I am calling
the White Sky. It'll happen over hours, or days. The system of
discrete planetoids that we can see up there now is going to grind
itself up into a vast number of much smaller fragments. They are
going to turn into a white cloud in the sky, and that sky is going to
"A day or two after the White Sky event will begin a thing I am
calling the Hard Rain.... It is going to be a meteorite bombardment
such as the earth has not seen since the primordial age, when the
solar system was formed," Doob said. "Those fiery trails we've been
seeing lately, as the meteorites come in and burn up? There will be
so many of those that they will merge into a dome of fire that will
set aflame anything that can see it. The entire surface of the earth
is going to be sterilized. Glaciers will boil. The only way to
survive is to get away from the atmosphere. Go underground, or go
The governments of the world frantically start to build a series of
ships using swarming concepts to evacuate the planet as much as possible...
"We are beginning to talk to our counterparts in other spacefaring
nations about creating an ark," the president said. "A repository of
the entire genetic heritage of the Earth. We have two years to build
it. Two years to get as many people and as much equipment as we can
into orbit. The nucleus of that ark is going to be [the ISS]"
"You want to use swarming behavior in the Ark?"
"The proposal is called the Cloud Ark," the president cut back in.
"And you have it correct. Rather than putting all our eggs in one
basket-....we will take a distributed architecture."