Like most American textbooks this is practical and well laid out. It includes sections on the construction of a good historical mystery and how to market it. It's biased towards the American market but has relevant, practical advice for all writers. A good entry-level text with useful advice about the choice of sources and research techniques, it also touches on the pitfalls which a new writer may stumble across and includes useful information about Internet and other resources.
Over many years of reading books on writing I've reached the conclusion that the Americans are hard to beat in this respect, and this book has only confirmed my opinion. The writing is very accessible, the advice extremely sensible. You can't ever get round the need to respect the old adage of 'seat of pants to seat of chair' but this book will certainly increase your chances for a successful outcome from your endeavours.