I found this book while rummaging around in 2nd-hand bookstores on Yonge Street (Toronto) last summer. I bought it, ripped off the cover and tossed the book in a recycling bin. I really doubted that a book based on an old TV episode would be any good, but you know what they say -- don't judge a cover by its book.
Update: It turns out that this book wasn't based on an episode. It's a spin-off story from the TV series. The author, Richard Deming, apparently specialized in these spin-offs. Also, he wrote ten books under the 'Ellery Queen' name.