People browsing books (be it online or in a bookstore) generally look at the cover first. If the cover grabs their attention, then they’ll read the title. If the title reinforces the cover or further interests them, then they’ll consider the book itself.
The other way people select a book is by scanning titles (be it by keyword or a list within a category). The title must capture their attention: making the book’s content clear, being provocative or intriguing, or demanding additional consideration. If the title does one of these things, then they’ll see if the cover reinforces the title. If so, they’ll give the book more consideration.
However, a lackluster title will end their deliberation; they’ll move on to the next title. Don’t let a weak, confusing, or unmemorable title get in the way of someone making a purchase.
You’ve worked hard on your book; work even harder on its name. After all, the title contains the most important words of your entire book.