Suppose that $X$ is a Banach space such that there exists a linear isometry $X \rightarrow X^*$. Must $X$ be reflexive?
Of course, this implies that $X$ is isometric with its second dual $X^{**}$. But with this alone it is not possible to conclude that $X$ is reflexive, James space is the famous counterexample for this. So a negative answer to my question should be at least as difficult as finding an example like the James space.. so probably not very easy.
No, consider $J\oplus_2 J^*$, where $J$ is a James space