Reddit reviews The Mabinogion

Ronald Hutton's Blood and Mistletoe

Really anything by Philip Carr-Gomm

A often-overlooked author, John Matthews. He has lots of books on Celtic shamanism and Druidry. A Celtic Reader, Encyclopedia of Celtic Wisdom, The Bardic Source Book, The Druid Source Book, and The Song of Taliesin: Stories and Poems from the Book of Broceliande just to name a few.

Also, if you haven't, you should read The Mabinogion for it's worth of Welsh mythology. I like the Jeffrey Gantz translation, but it's missing what I consider a crucial story prevalent to modern Druidry, the story of Ceridwen and Taliesin. You can find it in Lady Charlotte Guest's translation though, which is the original translation from Welsh to English.

Oh, and Joanna van der Hoeven's The Awen Alone. and I haven't read this one yet, but I read the author's other book, Zen Druidry. Both are short books packed with a ton of information, and the former is about practicing Druidry solitarily, something with which many of us here (and maybe especially you at the moment) can connect.