For further reading on all things Celtic:

The Magic Arts of Celtic Britain—Lewis Spence – Fascinating book with index.

Before Scotland – Alistair Moffat

Celtic Scotland – Ian Armit

Scottish Crofters – Susan Parman – Ph.D Thesis. Hard to find. Pub in 1990

Washerwoman at the Ford – Fiona MacLeod (William Sharp)

The World of the Celts – Simon James

Celtic Gods and Heroes – Marie-Louise Sjoestedt

Myths and Legends of the Celtic Race – T. W. Rolleston – Good place to start – no index

Superstitions of the Highlands and Islands of Scotland – J. G. Campbell – pub 1900.

Popular Tales of the West Highlands, Volumes 1 to 4 – J. F. Campbell – First pub 1890.

The Druids – Stuart Piggott

The Mabinogion – Lady Charlotte Guest. Also Sioned Davies (translation).

The Gallic Otherworld – J. G. Campbell – Taken from books first published in 1902

Daily Life of the Pagan Celts – 2009 – a modern approach – has index

Celtic Britain – J Rhys – 1904 – The reference for many of the others – Dense. Has good index

The Fairy-Faith in Celtic Countries – W. Y. Evans-Wentz – Dense. More for sampling than reading

Iron Age Communities in Britain – Barry Cunliffe – Huge book,  first pub 1974

Mythology of the British Islands – Charles Squire – a reference for many of the other books, yet very readable. First pub 1905

Celtic Mythology and the religion of the Ancient Celts – Dr Jesse Harasta – short book, lots of pictures.

Sir Gawain and the Green Knight – several

Le Morte d’Arthur books 1 & 2 – Sir Thomas Mallory. The English version of the Irish and Welsh gods.