i have used "Writing GNU Emacs Extensions" available here: https://www.oreilly.com/library/view/writing-gnu-emacs/97814... from a long time past for elisp programming.

mentioning it here in the hope that it is is useful to others as well...

it is also available as an ebook from oreilly: http://shop.oreilly.com/product/9781565922617.do

http://tuhdo.github.io/emacs-tutor.html#text-7-29 - the excersise:

    C-f to the beginning of each character group and add whitespace. 

No, don't! Use C-s or even better iy-goto-char (https://github.com/doitian/iy-go-to-char). This scales much better.

You can also set mark at first 'b' in the first line, go to first 'b' in the last line and use C-x r t to insert a string across all the lines.

You can of course use regex-replace, too: \(a+\|b+\|c+\|d+\) -> \1 <- space here

And so on and on. It's good to see well written "introductory courses", like this one, but what about "Emacs for black belts"? "Advanced Emacsology"? There is one book about writing Emacs extensions (http://shop.oreilly.com/product/9781565922617.do), but that's all there is. Does anyone know about another source of knowledge about the most advanced Emacs techniques?

What's wrong with the Giraffe Book? http://oreilly.com/catalog/9781565922617