They may have conceived an excellent program, but why don't they "sell" it technically with a good "How to install" Readme:

a) The folder disappears after installation and the first shutdown (only remains the Dock item if you thought about fixing it there).It's nowhere indicated this is normal. Also trying to install the folder in your applications folder fails: only an alias goes there which seems logical once you realize that the Dock item is the only thing that matters.

b) Safari MUST be open when you fill in the licensing information and press the "check licence info" otherwise you're not registered at BrainTickling's database and the infamous "please register message" remains forever across your Pdfs, etc.
Nothing's perfect: I now also had a Snapweb crash. Why?