Full review at my website by my team member. Here is an excerpt:

Plots improve as the series progresses. An intrepid native girl figures in each of their adventures (reminding me of C. S. Lewis’ “irrelevant young woman in shorts” who appeared too often in an old movie version of King Solomon’s Mines), who is probably supposed to broaden the appeal. But with or without the added female influence, many girl readers will enjoy these books as much as the boys.

Had a wonderful interview with this author on the entire series for Mountain Times Publications, a newspaper group in Northwest N.C. (20,000 print /1 million uniques): http://www.wataugademocrat.com/mountaintimes/columns/book_reviews/travels-with-hemstreet-asu-alum-s-search-for-adventure-turns/article_c9af5828-a3d0-51f4-923c-3336ce268abb.html