One significant contributor to SEO is meaningful link text. That's also a vital part of accessibility for people who must rely on screen readers.
Most screen readers let the user hear a list of links in the page, either in the order in which they occur or alphabetical order (the user can choose the order). So if all of your links are "Click here" — as in "<link>Click here<endlink> to order [title of book here]" — people who are visually disabled will hear "click here, click here, click here" when the list is read to them. If you leave out the "click here" and instead use "Order [title of book here]" as the link text, then people who are visually disabled will be able to find that link — and order your book — easily.
So meaningful link text is essential for accessibility.
Also, search engines determine page ranking by, among other factors, the text in links that point to the page. So if all your links to the page for ordering your wonderful book say "click here," search engines will decide that the page for ordering your book should appear in search results when people search for "click here." You probably want them to find it when they enter words in the book's title as their search terms. So let's look back at the wording on your page and see how you can make that happen. It turns out to be simple: Just make the link text "Order [title of book here]" — the very same thing you did to make your page more accessible.
And that makes sense, if you think of search engines as having visual, aural, and cognitive disabilities.
So the short answer is, "Believe it."