Marketing a Book - Goodreads Pay-to-Click

OK, of all the advice on Writing a Book that I have given, marketing is where I struggle the most. You can spend hours, days and weeks on this and your efforts may not show a return for a month. An example is changing your website where it takes a month to filter through to the search engines.

My recent venture into marketing is on Goodreads where I am paying for pay-to-click adverts. I have targeted fantasy fans mainly and my $90 stake is taking a long time to go down. Stats updates on my campaign suggest that I am getting lots of views, but the click rate is very low. If there are any sales due to the adverts -- I am not sure. There has been no surge during the campaign so it's difficult to gauge.

Goodreads recommend running a give-away at the same time and I did get a lot of people interested in the books (800 each and I only gave away 1 book).

Overall - not sure there has been any benefit. I have several ads running so there is some variety.

Some findings on the campaign:

1. The Omnibus edition-ad seems to do nothing, so not sure folk are interested in Omnibus editions.
2. Whether the pay-to-click is 50 p or 30 p seems to make no difference.
3. There is a complete month when no adds featured. Not sure how Goodreads select their ads but they seem to have forgotten mine
4. At the low level of statistics I am getting - no one ad seems to stand out.
5. I can only view one month at a time. It would have been useful to view the entire campaign on one chart

Overall, Goodreads ads seem very slow and not really worth the effort. I might be tempted with a pay-to-click on Google but my experience on Goodreads is not encouraging.

Anyone offer any comments over and above mine? What are your experiences?