Data on success stories?

Hi all

I've been listening to the audio book of Traction. It's great, but I have a question which I'm not sure is answered (note, I haven't finished the book yet).

He says things such as, 'find similar companies and see what they did'.

How am I supposed to know what advertising methods X company used when they just started out or what their landing page looked like.

For example, I want to create an e-book. Where would I find successful e-books (how do I even know how much it has sold?), where would I find out what their page looked like when it was new (maybe wayback engine?) and how can I find their marketing methods to get traction.

I imagine I just need to try and find articles about the subject, but is there any other way?

Thanks in advance