The only information we have for Valerius Maximus comes from his own writings. Therein he portrayed himself as a modest client of Sextus Pompeius (cousin to Pompey the Great and not to be confused with Pompey’s son), with whom he went to Asia Minor in 27 BCE.
Valerius’ only surviving work, and perhaps his only published work, is his Facta ac Dicta Memorabilia (Memorable Deeds and Saying), a sort of rhetorical handbook for students/orators. It contained examples of virtuous deeds sorted by topic (e.g. love between spouses, unwavering loyalty to friends, one more example) of both Romans and non-Romans (primarily Greeks, but some others, too).
The work was published during the reign of Tiberius, to whom he is very favorable.
Because of the nature of the text, it was often mined by later writers for stories and examples to shoe into their own works.