From the start of the Marian Army reforms to the accession of Spetimius Severus, H.M.D. Parker gives us every aspect of the internal organization of the legion s of Rome.
This is one of the best books on subject I came across. Is it somewhat dated? Could be, I am not sure to be honest. Lots of books I have read on the subject are more contemporary but, Goldsworthy aside, I do not recall any book with this amount of quotes and notes from other works.
Unlike Praetorians and Legionnaires, this is not just a view of historical movements of the legions and decisions that affected them from one Emperor to another. This is a book on Roman legions as they were, from very inception towards the times when they became more or less local militia (as professional as it was). I did not expect to read about the way how legions recruited and especially role and nature of non-commissioned and commissioned officers (it was interesting how master-of-camp was treated as end of ones professional career, unlike other primus categories that lead to further elite status) and professional elite evocati, training regimes and in general organizational and logistical prowess of the legion that ensured that while single legion can lose a battle, end up even destroyed, overall legion structure and very organization would always win wars.
Book is full of very minutiae of the legion's life - even from financial side, reasons for dissolvement for reasons of perceived cowardice and/or dishonor, role of standards, together with descriptions of the standard symbols and legion names, and that (at least for me) very complex and puzzling methods of assigning numerical ids - this book has it all.
Great book, highly recommended to everyone interested in military, and even general history.