How many books can we read in ancient greek?
What books can we buy now?
I know there are many translated books, but I don’t want them.
With the rare exception of books translated into Latin, Coptic etc and then lost there are at least as many books in the original Greek as their translations into modern languages. 
There is probably a whole lot that are still untranslated.
Thank you for your reply.
Then, how to get them?
We can’t buy many of them in a bookstore, can we?
On the Internet, I can’t make out which book is translated one and
which one is original one with notes.
That really depends on the bookstore. The bookstore I like going to has quite a bit: http://www.schoenhofs.com/
On the Internet, I can’t make out which book is translated one and
which one is original one with notes.
If it is not firmly stated that a book is in Greek it probably is not.
Thank you for your advice. 
I’ll try the bookstore.
Jacques-Paul Migne compiled two humongous collections of Latin and Greek Christian writings in the 1800’s, many of them still untranslated into English:
http://www.newadvent.org/cathen/10290a.htm
One can only see these volumes if one has access to a very good (monied) university. G&L scholars, who have easy access to all manner of G&L materials, have told me that one can find them at “any good university.” That may be true if one lives in Cambridge or in a “university town,” but for most of us, it’s too difficult to get close to a set. E.g., I live in Houston and none of the universities around here has a set. I’ve heard that a univeristy in Austin (a few hundred miles away) has a set, but I cannot confirm.
Bonum Fortunam, Amici.
There is also the Suda.
From SOL (Suda OnLine):
“The Suda is a massive 10th century Byzantine Greek historical encyclopedia of the ancient Mediterranean world, derived from the scholia to critical editions of canonical works and from compilations by yet earlier authors. The purpose of the Suda On Line is to open up this stronghold of information by means of a freely accessible, keyword-searchable, XML-encoded database with translations, annotations, bibliography, and automatically generated links to a number of other important electronic resources. We believe that greater accessibility of this material should facilitate a good variety of new research.”
I live in Austin, and though I’m not sure if The University of Texas, St. Edward’s University, or Concordia University has a set, the seminary I graduated from, Austin Presbyterian Theological Seminary, does–I’m not sure if it is complete, but if I remember correctly, it takes up a few shelves.