Although figure painting has been much better served of late, there have historically been few books that look at formal portraiture as opposed to the more popular style of a relaxed likeness. This is perhaps understandable as the classic style is seen as a specialised field requiring particular skills and maybe even equipment.
However, if you want to have a go, this book will help you considerably along the way. The introduction to materials and methods is comprehensive without being overwhelming and includes lighting, positioning the subject within the frame and how to evaluate skin colours. Chris also has useful advice on working from photographs, including what to aim for when you take them. In fact, the book has a neat trick up its sleeve in this respect, as each of the demonstration portraits is done twice, once from life and once from a photograph, and it’s interesting to see how this influences the result.
This is an American book and you should expect American facial types. I don’t mean that it’s outlandish, but there are some quite subtle differences that we don’t see this side of the Atlantic. This shouldn’t put you off, however, as the principles remain the same and, if you’ve followed what Chris is talking about, you’ll be painting your subject, not his.