Hi! If you're here, it's likely because you're curious as to what an author needs to do to gain notability on Wikipedia! Establishing notability for an author on Wikipedia is incredibly difficult, as you need to show that the author or their works have received coverage in independent and reliable sources. You can read a bit I wrote about sourcing here, but I'll try to go over some specific points about notability for authors and books.
Establishing notability
There are several ways to establish notability for an author (you can read about this at WP:NBOOK, however the two easiest ways will be to show where their work has been the subject of notable adaptations and/or that their books have received a lot of coverage in independent and reliable sources. The latter of the two is usually the easiest, as books (or other written material) are more likely to receive reviews than they are to be made into a notable adaptation. The difficulty level with adaptations is that you'd have to show where the adaptation is notable enough to where it'd pretty much warrant its own article - and not every adaptation gets the type of coverage needed to pass GNG.
Authors with only one book
Something to be careful about when trying to establish notability is whether or not the author is only known for one book. If the author has only put out one book of note and the coverage for them is solely about the book, it makes more sense to have an article about the book and not the author, as in that situation there would only be enough notability for one article: book or author. Incoming readers are more likely going to be coming in to read about the book, as opposed to the author, so it makes more sense to have an article about the work in question, especially as articles for authors who have released only one book tend to be extremely short because the coverage doesn't contain much (if any) coverage about the author themselves.
Authors with more than one book
If the author has released two or more books that have received reviews in independent and reliable sources, then that would establish notability for the author. Something interesting about this process is that while it's generally expected that each individual book would have its own article, this is not always the case. For example, John Smith wrote three books. Book A, received only 1 review, Book A received two reviews, and Book C ended up being his big break and received 10 reviews. In this situation his first two books might not necessarily merit individual entries, however the reviews for his prior work could help justify an article for the author. The same can be said for an author whose overall work have received reviews, but not enough to really justify individual articles for each book. Marta Acosta is a good example of this, as most of her books haven't received enough coverage to warrant individual articles for the most part. (Although this can, of course change over time.)
Self-published and indie authors
It's difficult to assert notability for self-published and indie authors because it's still possible for them to solidly fail notability guidelines even if the author has put out a lot of work and has a decent fan following, as the amount of work and the author's popularity does not count towards notability on Wikipedia. The reason it's so hard is because in most cases these authors will not have received coverage in the type of places that Wikipedia will consider to be reliable - and it's very difficult for these authors to gain the attention of the larger media outlets. Despite this, these authors still need to have received RS coverage that would establish notability. It's admittedly not entirely fair that we have to judge the notability of self-published and indie authors against the same criteria we'd use to establish notability for mainstream authors, but at present there are no guidelines that would be able to take any of this into consideration and it's unlikely that there ever will be. This doesn't mean that these types of authors can't be notable, but it does make it so unlikely that it's more common for these authors to fail notability guidelines than pass.
Sourcing
The trick here is that the coverage for the books has to be in places that Wikipedia would consider to be reliable. Trade reviews from outlets like Booklist and the Library Journal are usable, however they're not the greatest sources to use to assert notability for an article because of their short length. The best reviews will be in places like the Washington Post or the New York Times and will be at least 2-3 paragraphs long. General articles about the book are also usable as long as they go into a little depth and aren't just 1-2 lines stating that the work will release or announcing a cover. If these type of articles go into depth then of course they're usable, but most aren't. Ones that only list a press release or appear to be almost entirely based off a press release will very likely be considered a primary source.
Book blogs and social media sites like Goodreads cannot be used as sources. Sometimes, rarely, self-published sources can be used as a reliable source but you need to show how that source is considered to be a reliable and trusted authority. The problem is that few SPS receive the type of attention needed to assert this, as you'd have to show where the SPS has been routinely cited as a reliable source by reliable sources (academic sources, newspapers, etc). That's incredibly tough to assert.
Something else to take into consideration is that there are a lot of book review and award services out there that aren't usable. If the author has to pay to receive the review, it's not usable. If the outlet is one that openly advertises that it only issues 4-5 star reviews, you can guess that it's not seen as usable on Wikipedia. Vanity awards are also something to be careful of, as there are many companies out there that take advantage of authors in order to make a quick buck. However in general most book awards aren't usable unless you can show where the award/honor is notable enough to where it would likely warrant its own article.
