I've signed up to BookBub emails recently (if you don't know what BookBub is and why it's important for authors, have a look at this post 'HOW TO PROMOTE YOUR BOOK ON BOOKBUB') and now get daily 'deal' emails about the books they're promoting. Apart from getting cheap ebooks, the emails are super useful for learning how to write short blurbs or elevator pitches for your own books. Each book can only have a sentence or two to sell itself, like in a query letter. Well worth signing up to their newsletters to see how books in your genre are selling themselves! Two examples from today's email below, and you can join their list here.
Yes Bookbub is great although can be expensive to use. Has the biggest reach around the world and I think a good place to promote an earlier book in a series (at a discount) in order to find new readers for a new novel.