Nothing is True Everything is Permitted is a biography of Brion Gysin (1916-1986) - artist, novelist, poet and one of the collaborators with Sinclair Beiles on Minutes To Go.
As is usual with books dealing with the Beat Hotel and Minutes To Go, Beiles doesn't exactly take centre stage, but in this book he does get slightly more mentions. In addition to quoting Beiles, Geiger mentions that he was the author of several collections of poetry (usually only Houses of Joy - which was published in 1959 - and Minutes To Go are mentioned).
What is particularly noticeable is that his mental illness is not referred to, and overall there is a sense that Geiger treats Beiles with more respect than most Beat biographers.