TYPOS - and punctuation errors. If there are too many of these, I WILL flounce.
USE OF WRONG WORDS - Unlike typos, this is a deliberate and ignorant use of the wrong word by the author. I read a book once where on the first page it said:
"'Doddle' is a word my mom would use when she wanted to call me lazy."
No, 'dawdle' is the word your mom would use. 'Doddle' something you used because you were too lazy to look it up. In the UK 'doddle' means an easy task, but that is not what this author was trying to say.
INFO DUMP - I cannot stand when an author feels the need to give you every ounce of back story within the first 5 pages of the book.
COVERS - If your cover is childish, cartoon-y, or super bodice-ripper cheesy, I will NOT read your book.
YOUNG AND OLD LOVERS - I do not want to read about late teen/early twenty-somethings dating someone 10 or more years older. The younger the person, the less the age difference can be for me.
CHARACTERS - If you don't make me love your characters, I won't care about finishing your book.
ABUSE/ASSHOLE BEHAVIOR - I will not read books where asshole behavior is accepted and revered. There is an extremely popular book where the lead male is a jerk. He has not respect for anyone, even his love interest. While he has a sad back story, his behavior toward the girl is possessive and and easily forgiven. The lead girl sweeps it under the rug and lets his behavior develop into a completely unhealthy relationship.
LANGUAGE - No, not cussing, but overly flowery language or repetitive "hip" sayings. I cannot stand when a description of something in a characters mind doesn't match the character giving it.
NAMES - Unless the book is set in an alternate universe or in a foreign country, I expect to see some names that I recognize. If everyone in the book is, Skailar, Daxton, Raiden, and Obadiah, then I will stop reading.
CONSISTENCY - I saw a person who said that he was reading a western and then the pioneer woman put food into Tupperware. The words and actions have to match the world you have created.