Everyone swears by BookBub for results and they are all correct: BookBub is the king of the email newsletter industry. It has millions of subscribers where most companies have a few hundred thousand at most. It is a powerful website.
Which means it comes with a premium price tag.
If you are trying to promote your book on BookBub, even as a free listing, you should expect to spend a lot of money. And I mean a lot, like a few hundred. They break everything down by genre and pricing level. But, the thing is they are fully worth it. Scoring a BookBub is one of the most powerful ways to get a ton of new readers and hopefully sell through from one book to another.
They feature mostly high value titles, which means a lot of sales and a lot of reviews. This alone will be enough to keep many Indie Authors away, because even if you can afford it, the likelihood of getting picked isn't very high.
They don't take just anyone, and in fact, they won't even take great books all of the time. You send in for consideration (only up to a month in advance) and they decide if they are interested based on current market trends, editor preferences, and other features. They only take about 1 in 10 of all books submitted (and of those it is usually a lot lower for indie titles), which means you might have to try many times before finally getting picked.
You can also only submit once every month per author name, and once every six months per book. This doesn't mean it'll be impossible to get picked for a promotion, but it does mean that you'll have to probably submit a couple of times before they pick you.
Cost: BookBub is crazy expensive, and occasionally they adjust their prices upward. However, that is because they are constantly re-evaluating the prices to be as accurate and fair for the value. They are incredibly open and honest about this and very fair.
However, it'll be too expensive for a lot of people even if the ROI is good. Check out the pricing here to see where your book is going to fall, and then start putting money in the piggy bank for it.
They are worth it. I had a promotion for my book Raven's Peak and sold hundreds of copies, and that was only listed on Amazon. The biggest benefit is that they promote on multiple platforms, which means you can get some serious traction on a lot of different stores...or you can go exclusive to just Amazon.
BookBub is powerful, and even more so when stacked alongside other promotions. It is the cornerstone of any mega e-book promotion. When I did it, I used some other sites to get my ranking up a little bit before the promotion, and then let the promotion carry it to new heights.
I wouldn't recommend doing anything that isn't a first in a series, nor anything that is a standalone. Your best bet is going to be to offer a free promotion that ties into a larger series, because the sell-through is going to be huge. Best case yet: promote first book free on BookBub and then the second book discounted to lead people into a series.
My rating: This one is easily a 5-Star company and nearly impossible to beat. Submit every chance you get and keep trying for one, and then make sure you're ready to capitalize on it when you get one!