I'm not sure if it was necessary that I post a spoiler warning for a book almost 4 decades old. I sure thought it would be a hoot, though.
Anyway, it was a good read. My Dad just gave me a bunch of books that were his back in the 70s. SMD! being the first of them that I read. The first thing that strikes me about it (and the others) is how short it is. Only 118 pages in this book. I was able to breeze right through it. The story itself was solid with only a few gripes. My biggest problem with the book really had nothing to do with the story, but with Scotty. I don't think Mr. Blish did a very good job capturing Scotty's accent. It was nae impossible for me to read at times, and (to me anyway) seemed to come of almost more Irish than Scottish.
I like the idea of two Spocks, and how they argued and such. I was just surprised with all the other reference that were in the book (which were amusingly marked with asterisks) that Kirk's split into two by the transporter wasn't mentioned.
After I finished reading the book, I looked it up online. According to Memory Alpha, it was the first novel with an original story (as opposed to novelizations) aimed at adults. With that in mind, it certainly was an interesting choice to condem the Klingons to their homeworld for a 1000 years. Personally, I would have left more room for future use in sequals.
So what did everyone else think SMD!?