An interesting invited review of Miras is on the street in JAAVSO. Lee Anne Willson and Massimo Marengo's paper, published June 1 in JAAVSO, gives an overview of what we know about Miras, a little of what we don't (9% of Miras show period changes that are unexplained), and makes a great case for the continuing observation of these stars:
Nearly every observational study of galactic Miras includes reference to phases or light curves based on data collected by AAVSO or its sister organizations around the world... understanding how the Miras and their SR cousins are related will again depend on long-term observations and studies of bright, relatively nearby stars.
It's a handy factual reference for LPV aficionados and a nice introduction for anyone new to the field. You can download the PDF at: