dberube,
I think you would need to have a novel approach to make any headway in the registrar business, OR have a captive audience whose trust and business you already have (more than traffic, but actual business dealings).
IMO, currently, there is so much competition founded on "low price", that it wouldn't make a significant impact to be an "also ran" on that virtue alone (even though "price" is a huge draw). The registrar market looks even more "cut throat" than the PC industry. Companies like DirectNic made excellent headway by gaining customers when $15 registration was a "bargain". Now, GoDaddy has ridden its low price point, critical mass, upselling, and economy of scale to being
#1. They have used the "reseller" platform they run under WildWest Domains, and a different model of "discounting" (subscription) via BlueRazor to continue their march towards the height of success.
Good websites for research:
http://www.registrarstats.com/
http://www.webhosting.info/
http://www.icann.org/tlds/monthly-reports/
A number of registrars have tried to outright advertise "free domains" hoping to attract enough people that sign-up for for extended services. I'm sure the information on the sites above will testify as to whether the tactic proved successful.
An "affiliate" program would essentially be the same as a "reseller" program without as much teeth. One of the biggest draws for a registrar looking to capture reoccuring business, is to partner with hosting companies as their preferred service. Here is a registrar shootout from ISP Planet that analyzes a group of registrars and how attractive or unattractive their model appears to this group:
http://www.isp-planet.com/services/registrars/
Definitely something well worth reading even for general knowledge. If nothing else, it gives in some cases a candid view into the business considerations and program representations of some of the registrars interviewed.
Best of luck. Again, I think your best book is to sit down and brainstorm for a "novel approach" to the business. I think that will only be possible by finding an audience for domain names, a highly effective way of providing the product to them, and a good delivery mechanism. The more innovative the better. I'm a big believer in dark horses. Often the current players may miss an amazing angle that creates an opportunity. Without that however, I think the challenges of the business would grind against the financial incentive.
I think Fabulous has done a great job entering the market and providing very unique and appealing mechanisms for domain names owners with top-notch service. Moniker's nitch seems to be in paying close attention to security. eNom and Tucow have focused very highly on empowering their reseller infrastructure with highly flexible API driven systems companies can integrate transparently into their services.
~ Nexus