Its a pretty broad field. The couple of books I have that may or may not help are "Advanced Celtic Shamanism" by DJ Conway and "Dream Gates" By Robert Bruce I think its Robert Bruce. Any how these books pretty much cover a large playing field and do share details about other books that may or may not help you.
I like "advanced celtic shamanism" because it really is witchcraft worked into shamanistic principles. Although DJ's writting style and portrayal of Druidism are her own. "Dream Gates", in my opinion, is more about advanced shamanism. It works closely with altered states of mind, spirits, theories of other realms and technique.
I also have "Lucid Dreams in 30 Days, the creative sleep program" Its not shamanism persay but it will teach you, thoroughly, the art of Lucid dreams which plays considerably into shamanism.
But there are many books so don't stop with the few people name.
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