Facebook is indeed a great place to generate traffic and etc. but i had much more luck doing non smoking campaign with CPA and PPV landing page
I quit smoke 5 months ago I was smoking about 5 years. I will not smoke any more. I hate smoking. I know many things about smoking (peoples mistakes during smoking, people mistakes trying to quit and much more,), may post new topic about that.
Best bet is to find quit smoking article directories, and start giving useful hints on how best to stop smoking, also posting on blogs from addicts triyng to quit, can be beneficial, but you need to establish yourself as someone who knows what they are talking about before promoting your links
Promote it on facebook fan pages is the best I think.....just create a fan page with quit smoking niche...and attract so many fans as you can.....and then promote your website....
I'm pretty sure there are forums for "quit smoking" that you could post on, other than that take a crack at putting up flyers(hospitals, college, parks etc)
Watch the major media outlets and see what kind of smoking related stories they are covering, and write related or follow-up stories on your website. The reason this works is because people are actively searching for these trending news items, and you'll get your site up on page 1 far easier because there is less competition for trending stuff like this than your average search terms. As a result of the traffic, Google will start logging your CTR and bounce numbers, which are big factors these days, and as Google builds a history of data on your site it will climb in the ranks for all of terms your website is competing for. Google wants a history of data on you before they'll rank you on page one for anything significant.
As far as traffic goes it will probably be tough going the SEO route. I would go with forums and social media as has been suggested here already. You have to be subtle though and not out and out advertise. What to do when you get them there though? Make sure you get an email address by offering to share some amazing secret. Most people have tried to give up a number of times and are looking for a miracle. I don't know whether you can actually deliver this miracle though, but you should at least be able to get their email address by hinting that you can.
The best bet is to look for organic traffic and you can start with article marketing, submitting your site to various web directories, joining quit smoking communities and introducing your site. (Try building a content rich blog instead of a simple landing page, that will make you stand out of the crowd. The quit smoking niche isn't very lucrative/profitable if you're planning to sell digital downloads; it's just not worth it. Have a look in CJ (commission junction for some deals) and you be better of selling psihycal products instead of ebooks.