Jashmenn, I just checked it out.. good work!

how about very niche topics? I self published a book on Ruby regular expressions last month on leanpub, currently working on Python version of it. Later I plan on command line topics like grep/sed/awk/perl/etc one-liners and stuff like that (I already have lots of material on these topics as tutorials on github, need to convert to books)

Selling is the biggest pain point for me