Besides ordering John Bellair's Magic Mirrors, I ordered Tim Powers' The Stress of Her Regard (how could I resist purchasing a novel which takes its title from a poem by Clark Ashton Smith?), a supernatural "historical" romance, which details the interactions between the Romantic Poets of the early 19th Century (Keats makes a cameo in the novel, and Byron and Percy Shelley are fairly major characters) with a class of ancient, predatory elemental entities. Powers bases these vampiric beings on the nephilim of the Old Testament and the lamia of Greek legend. Powers portrays his nephilim as predators, but also as sources of inspiration (I'm about halfway through the novel, and Powers so far hasn't mentioned the Leanan Sidhe, the destroying muse of Celtic legend, but his "neffies" are a very similar concept).
The subject matter is also reminiscent of Powers' supernatural espionage novel Declare, which presents the role of similar supernatural beings in the Cold War (a trope employed by Charles Stross in such works as A Colder War). Powers also makes brief mention of fictional poet William Ashbless and Kusiak's tavern, from The Anubis Gates, one of my all-time favorite novels.