Interesting read that does what you expect it to do, but what it lacks in surprise, it makes up with thoroughness.
Idan Sherer, compartmentalizes the subject matter in a non surprising but adequate way; Spanish infantry recruitment, conditions of soldiering, combat and also includes the sack of cities and mutinies. Clearly Sherer does not stick to "accepted truths" like how the Spanish infantry were as described by Italian contemporaries to be lowly dregs, little better then animals but instead does his outmost best to de-demonize the Spanish infantry. He outlines their various background thanks to the preservation of several recruitment rosters, recruits that included former monks, Hidalgos and off course a lot of lower end persons, yet the diversity in background is striking and should be remembered when reading the opinions of Machiavelli who hated them so much. Even if at the same time (especially in the chapter on the sack of cities and their impact on local populations throughout the chapters) he does underline their brutality even if in most occasions German and Italian mercenaries were acting similarly. As Sherer notes, as much as the Spanish treatment of native americans, the Spanish sacking of Italian towns (Rome!)contributed to their overall bad reputation that was not quite undeserved.
Particularly interesting was the chapter on mutinies, Sherer correctly points out, the concept of a mutiny has changed, these days a mutiny is treason while for the Spanish Tercio's and their commanders and even the king himself; a mutiny was an acknowledged reasonable and to be expected response to the conditions the Tercio's had to endure. Conditions like inadequate pay, no pay at all, not enough food and bad leadership. I found it interesting to discover how the commanders and mutineers wrote polite yet firm letters as part of negotiations and both sides actively compromised, it had a so it seems a sort of trade union strike vibe. this comparing of the Spanish Tercio to modern armies is a recurring theme in the book, most of the times Sherer uses this to underline how harsh conditions were for the average soldier.
Sherer spent's a lot of time on the question whether if the Spanish army are proof that the seeds and origin of the military revolution truly lie in the 16th century. The answer is a yes/but at the one had the Spanish did introduce centralized bureaucratic recruitment, enforced a standardized equipment rule for their recruits and tercio's companies never fought against Spain even if they did mutiny at times when their (in theory) regular wages did not arrive. Sherer though notes that at the same time they still relied on plunder to keep the soldiers happy, they did not use formal "boot camps" to train new recruits as they were expected to learn while part of their company, they did no provide uniforms and all and all the battlefield would have been different but not alien for a Soldier of a few generations before them (even if gunpowder weapons had increased dramatically). So, a modern army? No but not quite a medieval one either.... Note; Something I do would like to see in the future; is how the Spanish army compares to the Swedish of the 17th century. Which of these two did have the biggest contribution to the setting of off the Military revolution that Sherer discusses and comments on? From a famous soldier point of view, the Spanish Tercio infantry companies were as (in)famous in their day as the Swedish hakkapeliitta cavalry units in their own respective battlefields. I believe this would make an interesting next study on the military revolution in early modern Europe.
In conclusion, it is perhaps not a book for a wide audience, it does require some knowledge on 16th century European politics and as with any specialized book it does expect a strong interest in one subject. But if you are interested in the early modern European history and want to focus on the military, this is for you.