Solnit has her flaws. She tends to make a mistake common among critics, that of confounding a powerful metaphor with literal truth. She sometimes over reaches. And I suspect that her research may get some details wrong.
That said, she is intellectually gifted, a good writer, has her heart in the right place, and is always interesting to read.
Read this book, and escape for a while the future that is rushing towards us with an earbud for a phone or Ipod always plugged in. There's great pleasure to be had in a contemplative walk---and in this book.