The "true" in Wright's title doesn't refer to the traditional kinds of scriptural truths we think of when we think of religions and truth. Wright is explicitly not interested in the traditional aspects of Buddhism as a religion. The book, for example, makes no claims about reincarnation or Tibetan rainbow bodies or the like. Instead, Wright wants to focus on Buddhism's diagnosis of the human condition. The part that is relevant to the here and now. It's Buddhism's take on our suffering, our anxiety and our general dis-ease that Wright wants to explore because that is where he sees its perspective lining up with scientific fields like evolutionary psychology and neurobiology.