A Pair of Cloaks

The first two CLOAKS books in one volume!
In Cloaks, called "a treasure" by Hugo-winner Mary Robinette Kowal, an old man in a small town hides a portal to another world in his basement. When Bess discovers it and goes through, she finds a world controlled by black-cloaked, knife-wielding horsemen called quistrils who have her on the run within minutes. Her only hope is to get back through the portal, if only she weren't already lost–and seriously ill, poisoned by local fruit growing in an orchard.

In Pandir Decloaked, Heldrick, a renegade quistril, is no longer satisfied with merely causing mayhem among the other quistrils. Due to Bess's influence, his goal now is to completely overturn quistril domination, a task which may take centuries to complete. But he finds it difficult being patient, and bit by bit his plans grow in scope while shrinking in timescale, and before long they include the unseating of Pandir himself, the current leader of the quistrils.

These two books are full of intrigue, suspense, and surprise. They will keep you glued until the last page.