Today is the last day of the month devoted to Poseidon and this post is about what resources I would recommend for someone just beginning to learn about him.
The first thing I would recommend is a good book on the Greek Myths. Poseidon is featured prominently in some of them. I would also recommend the classic writers Homer, Hesiod, and Pausanias. I recommend the Apostolos N. Athanassakis translations of both The Homeric Hymns and The Orphic Hymns because of a better translation into modern English that doesn’t used forced rhyme.
For a wonderful modern resource which includes works by multiple devotional polytheists, I recommend From the Roaring Deep which is put out by Neos Alexandria/Bibliotheca Alexandrina. In it you will find essays, short fiction, poetry, and prayers honoring or discussing Poseidon and the Spirits of the Sea.
Please note that in the interest of full disclosure, I do have an essay and a prayer included in this volume. However, as I have agreed to not receive royalties from this book, I do not feel that it is a conflict of interest for me to recommend it.