The Sorceress of Ambermere — J. Calvin Pierce

AN ORDINARY WORKING GIRL
... can burn out fast slaving her life away at a boring job in a drab little office in a big city Until a magical ring dispatches Marcia to another world.

AN- EXTRAORDINARY SPELL
... can wreak havoc when it's unleashed by a mediocre wizard--aptly named Rogan the Obscure.

She's an overworked, underpaid career woman suddenly imbued with awesome powers... about to embark on a journey through a mystical realm. With the help of a witch, a giant, and an enchantress, Marcia battles a demon--and fights to save humankind!