The single central conceit is outstanding and excellent hard SF, an interesting entry in what one might call 'time dilation horror'; there's only one central idea, however, which becomes strained with repetition over the length of the novel (as short as it is), and while I appreciate that Anderson tried to leaven the hard SF with real characters and interpersonal drama, I can't say he succeeded.

For punch, some of Larry Niven's Known Universe short stories using ramjets may be better ("Rammer" and "The Ethics of Madness" come to mind) and I would be remiss to not mention Peter Watts's "The Island" (suggested soundtrack: Cloud Cult's "There's So Much Energy In Us"), although Tau Zero is much more ambitious.