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I like BookBub a lot. You can choose what genres you prefer to hear about deals in, and they have a very rigorous selection process, so I rarely go wrong when I click on one of their offers. Another service I like is Book Barbarian. It's science fiction and fantasy specific, and it has a less rigorous selection process than BookBub. This can sometimes lead to some crappy books being listed in their daily emails, but it is good in that it allows you to see a lot of stuff written by newer and lesser known indie authors. I actually found my favorite book that I read last year on Book Barbarian. (It's called Clovenhoof, if you're interested. It's the hilarious story of how Satan gets kicked out of hell for failing to meet his quotas, and ends up living in London with a couple of quirky neighbors.)