"Who Got Einstein's Office?" Ed Regis, 1986. The descriptions of the most advanced computers of the day are, shall we say, quaint, and the author's writing style is slightly annoying, but there are lots of interesting details about the Institute for Advanced Studies in Princeton. A nice nerdy read, especially for a physics groupie.
"The Sherlockian," Graham Moore, 2010. Good idea, appallingly executed. The writing is ghastly, and the author did not do his homework -- in the first chapter, he says that a Victorian shilling was worth five pence, and he is completely clueless about the British class system or the women's suffrage movement of Doyle's time. I finished it but do NOT recommend it.
"The Bell at Sealey Head," Patricia McKillip, 2009. A terrific read -- well-written fantasy, one of those books that's nominally for "young adults" but rewarding for the rest of us as well. It makes me think of Elizabeth Goudge's "The Little White Horse" -- not the story per se, but the connection between the everyday and the magical.
Next in the stack: The "parasol protectorate" books that Laura mentioned.