Horse & Pony Books:
THE KELPIE'S PEARLS
ILLUSTRATED BY CHARLES KEEPING
Reprinted in the UK quite a few times n paperback by Puffin, Mammoth and Floris.
Also a large print edition published by Chivers.
First American edition published by Funk & Wagnals in 1964
Reprinted in hardback in the USA by Harper Collins
Reprinted in paperback in the USA by Avon.
The US editions had different illustrators: Joseph Cellini and Stephen Gammell.
EDITIONS PICTURED: 1st edition, Puffin paperback, Floris paperback, USA Harper Collins reprint, USA Avon paperback.
SUMMARY: Fantasy with some horse content. Set in Scotland near Loch Ness. Young Torquil loves animals and is friends with Morag an old woman the locals call a witch when they think she has summoned Nessie, the famed Loch Ness monster and brought tourists flocking to her door. But Torquil knows the magic comes from the kelpie, a supernatural water horse. Can the water horse's magic now restore peace?
THE WICKED ONE
(HAMISH HAMILTON 1977)
Reprinted a number of times in paperback by Methuen and Mammoth.
First American edition published by Harper Collins in 1977.
Reprinted in paperback in the USA by Harper Trophy.
SUMMARY: Fantasy tale with some horse content. Bad-tempered crofter Colin Grant is plagued by the Grolligan, a pesky magical creature who is drawn to Colin because of his anger. Meanwhile Colin's animal-loving son Ian also becomes entangled in the Grolligan's plans when he finds out his favourite filly is enchanted.
THE DAY OF THE UNICORN
HARPER COLLINS [USA] 1994)
ILLUSTRATED BY DONNA DIAMOND
Reprinted in paperback.
Not published in the UK.
SUMMARY: Unicorn story. Third in the Knight of the Golden Plain fantasy series about a young boy whose daydreams of becoming a knight magically transform him into Sir Dauntless, a fearless knight mounted on his black horse Midnight. In this story he sets off to capture a unicorn which has escaped from a tapestry. I don't think the first 2 books in the series have any horse content apart from that of the horse he rides.
To see the full series click here
The Kelpie's Pearls and The Wicked One were both published a number of times in the UK and the USA and are easy to find in both these locations. Also some copies can be found in Australia. The Day of the Unicorn was first published in the USA and has not been published in the UK as far as I am aware. It is therefore easier to find in America than here.