Ebook program

Adwords is charging outrageous bid amounts for many of my keywords even $10 minimum for 4 – 5 keyword phrases so I need some very good alternatives that will drive targeted traffic to my site. I don’t like Yahoo search marketing (too complicated). My site is an eBook site.
My site is http://www.kissmyebook.com

I’m reading an ebook online where the site creators put a space for people to comment on each paragraph. I’m really enjoying reading the comments, but the site only has one book. I’m wondering if there any other ebook sites like that.
I mean out of copyright ebooks that have been published. Like The Scarlet Letter or Jane Eyre.

I’ve got several files from my divorce paperwork that are scanned as PDF files, but I want to combine them into one easy to read ebook. How can I do it? Something simple since I use a MAC.

Are you an affiliate with Clickbank or Paydotcom? Have you ever promoted an ebook?

If so, I’d like to know what your initial criteria is for selecting an ebook. Do you look to be familiar with the subject? Do you look at the commission only? Do you look for a professional looking vendor website first, or it does it matter at all? Are there subjects you don’t promote?

These are general knowledge questions so you get the idea of what I’m after. I’m looking for the “current state of the art” of ebook promotion. I’m not really looking for freebie methods, or list gathering techniques, or things like that. I’m looking for the information that helps affiliates decide whether they would or would not choose to push a specific genre of ebook (regardless of what that genre is).

If you have some experiences and specific web pages that are still up and active for show-and-tell (I know this is a fickle market and websites sometimes don’t last), please share them here.
I appreciate the great answers so far. I’m learning about the promotion side of things and you will have guessed by now that I’m in the process of writing an ebook. This gravity concept is interesting but seems to have proponents and detractors also. I just found this interesting discussion about this topic…. http://www.warriorforum.com/main-internet-marketing-discussion-forum/104186-do-high-gravity-clickbank-products-always-convert-best.html
While we’re on the subject of both Clickbank and Paydotcom, how do I get affiliates from both sites on-board? Isn’t the ordering button (on my future sales site) made for one company or the other? Does this mean that if I pick CB then I can’t go with Paydotcom? Is it important to pick one or the other early on, or is there a way to have both on a sales page?