Membership website based off a book someone else wrote.

Titles of books aren't copyright protected, and neither are facts or ideas, and sounds like you've done a substantial amount of work automating these formulas and building on the ideas contained in the original book.

But is your intended website an infringing "sequel" that re-tells the original content, or a non-infringing transformative new work that updates and expands on the original? It's impossible to say without reviewing the original book and your intended website. and how much is actually copied.

Same problem with your domain name and website. You clearly want to use this original book's title and content and trade off it, even using its title as part of your own domain name. This requries an analysis of whether your content is "substantially similar" to the original work.

Your intended use of the book's title in your domain name may unfairly compete with the book. And if the original work's author has trademarked any mark (contained in the book title) for investment services, you may be infringing that mark.

You need to consult an IP lawyer to disclose what you plan to do and the original work so you can get some specific advice.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

Seems to me the issue is whether you may lawfully sell a service that automates the task of completing someone else's investment formula.

Copyright does not attach to the process of doing something -- in your case, the process of working through an investment formula. Nor does copyright attach to the process instructions. The "investment formulas" in the book, therefore, are unprotected under copyright law. And so, under copyright law at least, they are free for all to use (and automate).

For quite some time, however, the process of doing something -- even if not automated and even if divorced from any machine or device -- was patentable (though no longer). There are many, many patents in the investment field directed at how to go about working through investment formulas. See, for example: http://bit.ly/14IDYy Before you automate someone else's investment formula you need to investigate whether that process is patented.

As for using any reference to the book from which you gleaned the formulas, that is a very bad idea -- even if more facts tend to show that such use is potentially lawful, you will most certainly raise the ire of the author and/or publisher. And then you'll have to fight a peripheral battle that distracts you from your goal of selling your service. Speak with an intellectual property attorney. Good luck.