There's also an odd algorithm at goodreads on how your book gets shown in recommendations; a part of which is based on number of times members shelve your book on a genre-matching shelf name (I think, I never fully understood it and currently recommendation pages are having some bugs).

Surprisingly few goodreads authors shelve their own books other than on the default shelves (read, to read, currently reading). One person only shelving a book as say "horror" isn't going to push it to top of recommendations. But, members glancing at book page would see that someone thought it was a "horror" book. And goodreads groups that do odd challenges, book of the month reads, buddy reads, penpal reads, etc. frequently specify a particular shelf gets used—another free way to get book out there (not likely big results unless lots of members shelve because when groups click a shelf the books with the most members shelving show first so a book only shelved by the author ... but every bit of exposure and discussion helps).