The pretext for this book is rather slight – one of the significant volunteer contributors to the Oxford English Dictionary was, although an intelligent and educated man, also an inmate of an insane asylum, confined for a murder committed while in the throes of a schizophrenic paranoid delusion.
While, as a revelation, this fact may be less than earth-shattering, Winchester uses this story of the inmate, Dr. W.C. Minor, the man he killed, George Merrett, and the main editor of the OED, Dr. James Murray, as a vehicle for all kinds of interesting details – he goes on quite a number of tangents, but they're always immensely well-written and fascinating! Winchester isn't afraid to stray from dry, historical writing – he definitely makes guesses, fleshes things out for colorful effect – but his research is also obviously thoroughly done, and he also stops short of fictifying (ok, that's not a word, but I think it should be) his topic – it's always made clear when his scenarios are theoretical.
I'd highly recommend this book not only for those interested in dictionaries and lexicography, but for anyone interested in Victorian England, the Civil War, treatment of the mentally ill, or any of a number of other topics.