Wordiness or overwriting — the book is not excessively wordy, particularly, no rambling descriptions, dumps of information, unnecessary repetition or irrelevant scenes.
As I kid, when I envisioned a writer, I saw someone who was very learned and they used long and complicated words. They might even smoke a pipe and wear jackets with patches on their sleeves. (Ahh, the mystery of childhood misconceptions.)
Some of my first writing was a game to show how smart I was with my vocabulary. I'd work every long word I could into my stories.
Well, I got my own education on that approach when I released a mystery novel I was working on to a group of beta-readers. One of the common threads of the critiques was that the book was "too wordy" and it "seemed over-written." Other friends said I used too many long words, too.
That stung. I worked really hard at being smart with my book and it back-fired. (It didn't help that the front end of the book was ponderously slow.)
I've learned since then that I don't have to write 'dumb' or talk down to my readers, but I don't have to try to impress them with my vocabulary. Writing clearly and succinctly seems to better connect with my readers. Since I write in genre fiction, this even more important.
Now, this doesn't mean that your book has to be dumb. Not at all. Readers love smart books, but over-smart writing doesn't always win them over.
So, the next time you decide to try an impress your readers with how smart you are, think again.