Ask HN: how can a small book suggestion site make money?

The most obvious approach would be affiliate links. I'm not sure that it would be the best, however.

foxblot does use amazon affiliate links

The creator of http://anynewbooks.com/ is an HN regular - so hopefully he'll comment - and that service is similar to yours. I'm pretty sure he only uses Amazon affiliate links to make it pay.

Check out http://hn-books.com/ created by this forum's own DanielBMarkham

have spent some time tweaking the algorithm for relevancy.

the thing that i find most annoying at this point is the slow speed