Of ousia of AIN, nothing cannot be said, for it itself is not.
At least, until it begets and is. Jokes aside, there is a lot,
and nothing much to say about concept that cannot be
understood nor defined by human mind which lives inside of it.
But let us ignore the statement above, and say something about
it. According to Lon Milo Duquette, Nothing is the creator
of Reality.
"The first thing that attracted me to Qabalah as a young
Chicken Qabalist (hatchling) was the concept that everything
proceeded out of this "Nothing". That made Nothing the
ultimate creator, not the Elohim, or Jehovah, or any other
ill-tempered bullies of the Old Testament. I liked the idea
of brooding and inscrutable Nothing behind everything in the
universe." Lon Milo Duquette-Chicken Qabalah, 7th command-rant
Qabalist teaching about AIN is as such, that there are three
kinds of nothing, which are:
- AIN
- AIN SOF
- AIN SOF AUR

The first kind of Nothing, The AIN, is the kind which is not,
it is not even the concept of non-existence. AIN is the
notion of absence of anything including itself.
Now, if AIN continued its non-existent existence you would
not be here reading this, but you are here, pretty convinced
of your own existence. That is because AIN realised itself in
the Law (Lex) into its second kind - AIN SOF.
AIN SOF, The Limitless Nothing, the Autogenes, came to be
after AIN realised by Law, that it does not exist, and that
realisation "popped" it into existence, thus creating the
understandable and definable concept of Nothing, which you 
know of. But Law is such that there cannot be a reality
which is full of Nothingness and thus by Law AIN SOF
realised the perfect Notness of its Nothingness evolving
into AIN SOF AUR - the Limitless Light. And it was happy
with its new form for Nothing is Not! And if Nothing is Not
then due to the negation, Something Is! And that something,
the light in the vastness of AIN SOF, is the beginning of
the universe, which is still contained in its non-existent
reality of AIN. Ex nihilo nihil fit.

To gain deeper knowledge of AIN, I recommend reading
Lon Milo Duquette's Chicken Qabalah.