My habits are changing. I used to prefer longer books on the basis that I was getting more pages per dollar. Now, however, as I am trying to expose myself to a variety of self-publishers, shorter works have a bit of an advantage. On the other hand, one of the very memorable books from my youth, Ursula Le Guin's The Beginning Place, is quite short. On the shelf, though cover art gets my attention, it's more the copy that makes or breaks the deal.
I do pay attention to reviews, but I almost ignore the average number of stars on any kind of fiction. I first read a selection of 1-star and 5-star reviews to get my impressions from each extreme of the appreciation spectrum, and if my interest persists, some of the ones in between. A review that mostly whines about delivery, or says the book is great or terrible without bothering to mention why gets tossed out up front and I move on to the next.