In the beginning... the first Python book started, 
during the Python 1.X era (1.2 and 1.3, to be precise).
It was signed in 1995, after months of convincing the 
Perl-focused publisher (then, O'Reilly & Associates) 
to take a risk on an 
_<A HREF="https://learning-python.com/python-activities-history.html#1996">upstart_</A>.

This was the first of 15 books and 12k pages to come.
It begat both _<I>Learning Python_</I> and _<I>Python Pocket Reference_</I> 
(ahead); essentially, two of its appendixes were split 
off into standalone books.  My optimistic sales estimate 
in 1995 was 5k units, but by 2020, this title and its
progeny crossed the 750k mark.  Takeaway: I'm lousy at estimates.