Ann Wigley wrote her first book, The Red Horse Haunting, for the J A Allen Junior Equestrian Library. She helped with the local Pony Club and ran a livery yard, and wrote the story while recovering from an operation. She only sent it to the publisher because her daughter insisted! Since then, she has written a story for Stabenfeldt. This is a good read: the only odd thing about it is something presumably visited on it by the publisher. The story is set in England but has odd Americanisations, presumaby to make it more acceptable to its target audience.
Finding the books
Both books are generally easy to find, and not too expensive.