Prima facie, James Blish's Haertel Scholium presents a mini-multiverse, its four divergent branches dealing respectively with telepathy, energy beings, the Dirac transmitter and the planet Lithia. (The single Lithian novel is also Volume III of After Such Knowledge.) However, the Dirac transmitter "branch" denies that there are "branches of time." Its protagonists work to ensure that they continue to inhabit a single consistent timeline. So maybe the alternative future histories of the Haertel Scholium do present mutually incompatible fictional narratives?