"Mark Phillips" was the pseudonym of two well-known science fiction writers: Randall Garrett and Laurence M. Janifer. Their joint pen-name, derived from their middle names (Philip and Mark), was coined soon after their original meeting, at a science-fiction convention. Both men were drunk at the time, which explains a good deal, and only one ever sobered up. A matter for constant contention between the collaborators was which one.
They collaborated for some years, and devised an interesting method of work: Mr. Garrett handled the verbs, the adverbs and the interjections, Mr. Janifer the nouns, pronouns, and adjectives. Conjunctions are a matter of joint decision, and in the case of a tie, the entire game was replayed at Fenway Park, Boston, the following year.
Regardless of who wrote what, Brain Twister is a highly enjoyable novel about spies and telepathy, as only two great writers could have conceived it!