I like the FussyLibrarian. They are easy to use and professional and their book promotion email mailout is easy to read on computer and mobile.
Their costs are very reasonable and I've had a good rate of downloads following promos with them.
Last time I checked, you need ten reviews with an average of 4 stars for them to take your book.
If you're looking for more reviews in general, then I also use LibraryThing. There are some constraints to signing up to their Giveaway scheme - you can read all the details on their site. Basically, you give away a copy of your book in exchange for an honest review.
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