Futuristic: books whose plot is based in the future
Time travel: books that tell a journey through time
Steampunk
Paranormal: books with fantasy elements (that are not urban, epic or romance)
Magic: books where magic is a heavy player
Superhero: books of superheroes
Terror or horror
Gore: books with a little extra in blood and guts
Dark: books that show the worst of the human nature
Regency: books about nobles from the Regency period
Ancient history: stories during the ancient times
Classical: stories during the classical period
Middle ages: stories during the middle ages
Ménage: romance and erotica books with group sex
BDSM: books that disply BDSM practices
Rape: books where a rape takes place
Kidnap: romance books where one of the main characters is kidnapped by the other one
Cheating: books where a character cheats on their love ones
M/M: books that tell a love or sex relationship among men
Friends to lovers: romance books with friends falling in love
Enemies to lovers: books with enemies falling in love
Second chance: romance books were the main couple is taking another shot
Age gap: books (usually romance) where the age difference of the main characters is important for one or both of them
Faking: books (usually romance) where a couple fakes a relationship
Undercover: books where one or more of the characters goes undercover into some dangerous organization
Arranged marriage: books where the main couple is forced to get married
Secret kid: books (usually romance) where the characters discover they have a secret kid
Love triangle: books where there is a love triangle or even a polygon with more sizes
Warriors: books (usually romance) featuring warriors
Pirates: books (usually romance) featuring pirates
Highlanders: books (usually romance) featuring highlanders
Angels: books (usually romance) featuring angels
Demons: books (usually romance) featuring demons
Gods: books (usually romance) featuring gods
Vampires: books (usually romance) featuring vampires
Shifters: books (usually romance) featuring werewolves, weretigers, werebears…
Aliens: books (usually romance) featuring aliens
Cyborgs: books (usually romance) featuring cyborgs or enhanced humans
Sports: books (usually romance) featuring athletes
Students: books (usually romance) featuring college or high school students
Soldiers: books (usually romance) featuring soldiers
Rockers: books (usually romance) featuring any kind of musician
Racers: books (usually romance) featuring professional racers
Bikers: books (usually romance) featuring bikers
Fighters: books (usually romance) featuring professional fighters
Celebrities: books (usually romance) featuring somekind of celebrity not mentioned in previous categories
Bodyguards: books (usually romance) featuring bodyguards
Firefighters: books (usually romance) featuring firefighters
Detectives: books (usually romance) featuring cops or private detectives. Law enforcement in general
Doctors: books (usually romance) featuring doctors, nurses, paramedics or similar
Thieves | Con artists: books (usually romance) featuring thieves or con artists
Cowboys: books (usually romance) featuring cowboys
Businessmen: books (usually romance) featuring businessmen or businesswomen
Billionaires: books (usually romance) featuring billionaires
Royals: books (usually romance) featuring members of a royal family
Bad boy: romance books featuring the classic bad boy
Bully: romance books featuring bullies
Grumpy/Jerk: romance books where one of the main characters is the classic grumpy or jerk one
Ex-con: books (usually romance) featuring an ex-convict
Murderer: books (usually romance) featuring a murderer or psycopath
Mafia: books (usually romance) featuring mobsters and mafia-related characters
Criminals: books (usually romance) featuring any kind of criminal
Assassins: books (usually fantasy) featuring professional killers
Hitmen: books (usually contemporary) featuring professional killers
Escort: books (usually romance) featuring an escort
Stepbrother: romance and erotica books where the love interest is among stepbrothers
Single parent: books where one of the main characters is a single parent
Widow: romance and erotica books where one of the main characters is a widow
Boss/Employee: a book with a love/sex relationship between the boss and an emplyee
Teacher/Student: a book with a love/sex relationship between a teacher and a student
Anthology
Comic
Scary: any book that makes me feel fear
Cliffhanger: those endings that give heart attacks to readers
First person: books written in first person
Nerd: most likely only suitable for nerds
Giveaway: book I won in a giveaway (which means I didn’t pick it)
Free: book that was free in Amazon, Bookfunnel or similar. This usually means that I only looked at the price tag, so… anything could happen
ARC: copy of the book given freely by the publisher or author in exchange of an honest review
Gold star: book that will always have a special place in my shelf
Teach: books that try to teach something while telling a story
Tears: books that make me cry (which is good)
Hot: books with really good love/sex scenes
Sweet: books with sweet moments between the characters
Book boyfriend: romance books with a guy that you would steal for yourself
Great cast: books where you will find great characters wherever you go
Frenzy: non-stop action that makes a book better
Funny: books that make me laugh
Great worldbuilding: books where a fictional world full of lore is created
Boom: books with a shocking twist
Nail biting: when you can’t set aside a book, no matter what
Great cover: books with a really good cover (review edition)
zZz: boring books
Weak: books that feel rushed and lazy
Lost: books where I get lost in the plot due to the author’s style
Bad style: when the author’s style annoys me
What?: those books that push hard to believe situations
Love?: strong romances that are hard to believe
Incest: just gross
Bad sex: sex scenes that make me uneasy
Angry: books that piss me off
Cliché: books with obvious clichés
Fumes: smoking is gross, so if a book has too much of it, its mark will be lower
Drugs: books where drug abuse is normalized. Say NO to drugs!
Bad cast: books where most of the characters are forgettable or a pain to read
Bad cover: books with really bad covers (review edition)
Burn: a bit drastic, but some books don’t deserve my shelf