Hmmm......... IMHO, I think website conversion (rate) is an area that includes multiple factors for success.
Remembering that conversion does not always require a sale. As long as the visitor performs the most desired action, you have a conversion.
Off hand, I thought the following might be important for conversion:
1. Web Sales Copy aka is the copywriter's (which could be you) work any good?
2. Website navigability (if applicable) and ease of use (those 1 page salesletter websites obviously don't count).
3. Appearance of the website and its ability to convey credibility, reliability, and relevance to the visitor. This could include graphics and color schemes as well as their placement.
4. Point of entry to the website, or more specifically the landing page. For example, did the visitor arrive on the website landing page from a PPC ad? If yes, how was the ad text framed to prepare the visitor to be in a more responsive mood.
5. Presence or absence of effective "engagement" devices (e.g. audio, video, a topic/market relevant survey etc.) in the right context. Of course, some folks might argue that these features actually turn people off.
Just my 2 cents worth'
Please add or comment further
Cheerio

P.S. What I meant to say was: There might be more than 1 book or 1 area of expertise that you'd need to seek out.
