It's part of an ongoing promotion, where a new selection of 100 ebooks goes on sale each month. The discounts last until the last day of the month.
Many of the titles of priced under $3.99. I purchased The Girl in the Gatehouse for $2.99 and Iris Johansen's This Fierce Splendor is $1.99.
Here are some of the Kindle books now priced at $3.99 or less:
|"Girl in the Gatehouse"||$2.99|
|"The Silent Governess" $2.99|
|"This Fierce Splendor" $1.99|
"Don't Say a Word" $1.99