Any genre of fiction is acceptable. Non-fiction is also acceptable if it is on a subject of general interest and targeted at a layperson.
The book must be Available as an eBook from Amazon.com.
The book must be “indie published.” Our definition of indie is very broad. Self published and small presses are in. The Big 6, their many imprints, and the largest of the non-Big 6 publishers (Harlequin, for example) are out. However, if your book was previously published by one of those publishers and you’re now re-publishing it as an indie, you’re back in.