I am working on the service which allows blog owners to distribute their content in a printer form by regular mail. Every blog reader will be able to subscribe to his favorite blogs and receive it as a newspaper.
1) How can I do a marketing research to see how many people are ready to use it and how much they are ready to pay?
2) How can I evaluate the market size for this service?
I would ask blog owners to run a poll on their website. Exchange free advertising in your newspaper for them running the poll for a week and sending you the results.
You can also create a website for your idea, and run a poll/survey on it.
Here is what I could think of while approaching this :-
That will give you a good idea of how many people buy books based on content which primarily originated from blog posts.
Hope this helps...