Masno is the same word as "The best".
You can use this for example: Wow, 2 days ago I bought an money making ebook and this is very masno!
If something is really very good you can say "Masno w ciul"
You can use this for eg. : I saw money making method in Monetizing Section, this is Masno w ciul !
("Masno" is polish word)