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It's likely that your competition is going to be a mix of large book sellers, online outlets, the author's or publishing house's pages or sites, review sites (after the book is released - and this can include major newspapers and magazines). You can get a good idea of who these are actually going to be by looking at the author and publishing house and searching for books they've published in the past. What do those SERPs look like? Getting in first with a landing page on a good website is a good piece of the battle, so definitely create your pages about the book early. If there are press releases or interest from readers in the lead-up to the release, your site should be one of the only resources ranking early if you get in before the big retailers and newspapers. Amazon is particularly strong for some book queries, but Google would ideally prefer to rank diverse websites (not three or four Amazon URLs on the first page, which I have seen happen for book names).