There are many views on having a book trailer or not having one and it is a personal decision. Many book trailer companies make very high-quality trailers, and some do actual film trailers to excite people’s interest in your book. The biggest problem with the actual film trailers is they are so pricey that it will make one think twice or three times about having a trailer. They can run more than 1000 dollars. Yes, it would be wonderful to have that kind of trailer, but you would probably be as well off to promote the trailer through social media, even if it means spending a few dollars on that promotion.
These trailers have as much chance of having people view them as do any other trailer.
One thing to keep in mind is that the days of just a slide show of book photos and a few interesting transitions from one slide to another are gone, make sure you pick good music, have something in the intro to draw potential buyers into looking at the trailer and with luck buying your book. Put it up on your website or FB author page, pin it to the top of the page, and above all talk about your book.
Some authors are doing videos to sell themselves instead of their books, this can be a good thing if you are branding yourself as an author but keep it to Instagram or another short format. Above all keep the trailer short, all too many lose interest after a few seconds or a minute, unless the music fits the trailer, and enough is going on that your prospective buyer forgets the time when watching the trailer.
Along with the more traditional trailer, there are now teasers both animated and filmed. A book trailer is an excellent way to promo an up and coming book, to get the interest of buyers before the book ever hits print.