Although there are many "one hit wonders" in terms of authors, some deliver consistently.
In my opinion, these authors are ones who you can count on to deliver an enjoyable read.
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Mary Higgins Clark- Though her books are extremely similar, so much so that I have read almost everything and can't keep them apart, her works can be counted on to provide entertainment in terms of the suspense/mystery genre. In particular, I enjoyed
Where are the Children and
All Around the Town.
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Tamora Pierce- Tamora Pierce is a good read for fantasy. Her series include The Immortals Quartet, The Song of the Lioness, Protector of the Small, Trickster, and Beka Cooper. These books are labeled YA but they are quick and enjoyable reads.
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Robin Mckinely- She has numerous other good reads besides
The Blue Sword. She writes a more adult style of consistently high quality fantasy.
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Sarah Dessen- This author is consistent in her mediocrity. However cliche and feminine her books may be, they always deliver a good read if you are looking for mindless literature that still has good character development and an engaging plot.
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Dan Brown- His books are always action-packed and suspenseful with frequent surprise endings.
Though I am sure there are authors I am forgetting, this is all I can think of at the moment.