The directories include a set of links around themes. A directory is more specific, the more visibility it may be attractive to a seller because the traffic can become very skilled. However, it should be understood that the traffic generated is important ...
The remuneration policy to directories can be given that conventionally all affiliates, or in rare cases a mixed fixed cost of attendance at some cents per click.
Please note that the presence of advertisers through affiliation in these directories does not benefit from the valuable backlinks and thus boost its SEO, as well as the links generated are not "hard", but go through a tracking code.
Effectiveness of affiliation directories today
Directories are becoming less effective, because of past abuses.
Indeed, Google has penalized many books that came to position themselves very well in search engines.
Of course, there are still some excellent books that will fit perfectly to your target.