Try to rank for other keywords. Just replicate what you did to rank #1 for your primary keyword. Looks like you've already reached a level that 90% of other marketers fail to reach. Now it's time to duplicate it over and over again.
Yeah I guess I'll have to do that. Problem is that the site currently only focuses on fantasy books and i'd have to expand it to another domain and go more global. Or a new website, im not sure yet. On books, fantasy books.
who say's you need a new domain to cater for more generalised information about books? Also share the link.
If you have got a budget to work with you could try CPA marketing with an ad on a high traffic site and link to your site. Don't know your niche that well but is there a chance to link on some forums. Have a look at Forum Finder and search for your niche eg "fantasy + Niche + Forum". Is your niche big enough to expand on and make more money? It would also help if we had your domain name to see your site details and optimization.