This is an up and coming company that is trying to make a name for itself in this overloaded market. It has done a decent job up to this point of building an audience, and it has actually been working very hard recently on bringing in new readerships that might be interested in hearing about free and discount books.
The catch to this is that they have been reaching out to authors with fairly large followings to build this audience, which might come back to bite them. First off, they are focusing very heavily on twitter to showcase large numbers of followers, but we all know that Twitter engagement is very minimal. And, even worse, they are relying on followings that aren't necessarily targeted toward a particular audience.
This is another genre specific newsletter that caters a lot more toward science fiction and fantasy than toward contemporary or literary fiction.
Basically...It has to be on sale, has to be a real book, and has to have at least ten (positive) reviews. A few of their requirements are vague, meaning they could reject you if they don't like your cover, but in general if you meet the numeric requirements you should get in without problem.
You are invoiced, not paying up front, which means they actively screen books before promoting them which is something I like.
They aren't as expensive as a lot of locations, but they do have a tiered system where you can buy the 'base' package plus addons that will help increase the reach of your post. I wouldn't call them super expensive, but there are certainly cheaper options out there.
Their prices also change fairly rapidly, which could be cause for concern (but not compared to somewhere like Online Book Club that changes wildly without provocation or proof of results.)
I've used them about five times, and I'm yet to make my money back on an advertisement. That being said, I'm usually within jumping distance of at least breaking even, which in certain cases (especially a new release) is pretty good. Sci-Fi seems to perform decently well, but the audience is fairly static so I wouldn't promote here too often with the same book. Make sure to mix it up.
They have some decent deals for authors, including a built in loyalty program that is kind of cool. Basically, you submit to them over and over again and after a certain number they will make it a free promotion rather than invoicing you. This isn't something you can look up, but rather something they keep internal.
It is a friendly and sleek website that looks quite nice. It is easy to submit a book and doesn't take very long, nor does it have some extra ridiculous sizing requirements on images, etc. They certainly built their website using modern techniques.