A few things frustrate me when I read a book. Conversely, these are a few things I try to avoid as I write.
#1: Using passive or stative voiced verbs when an active verb is available.
#2: Using prepositions after verbs when they are unnecessary.
#3: Using numerical lists that only have one point (i.e. “first” and no “second”).
#4: Prepositions appearing in the middle of sentence, when not for emphasis. I.e. “He went over the fence for fun to see the people.”
#5: the Absence or overly profuse use of “therefore,” “thus,” “so” and the like. Use them when appropriate but don’t overuse them.