This book by Piers Paul Read is a bit of history written in an excellent narrative style. A type of writing normally referred to as a 'popular history'. The author covers much more ground than just the "Temple Knights" and it makes a good introduction to the Crusades. In fact, the author starts his narrative by going all the way back to Abraham and his near sacrifice of his son and explains the historical reason why Jerusalem and the Temple mount are important places for Jews, Christians, and Muslims.
The Templars were started after the success of the First Crusade as a way providing protection for pilgrims on way to the Holy Land. While not the first religious order to be allowed to engage in military action (the Hospitalliers proceeded them), they were the first religious order specifically set up as a military order. Founded in 1119 by the efforts of Hugh of Payns the order took its name as 'The Poor Fellow-Soldiers of Jesus Christ'. King Baldwin II gave them room at the former al-Asqa mosque built on the traditional site of the Solomon's Temple. Because of their location, the order eventually became known as the "Knights of Solomon's Temple", or the "Templars" for short.
The "Templars" was a true religious order with its members taking vows of poverty, chastity and obedience. Eventually the Templars were bound to follow the Rule of Benedict modified to take into account the peculiarities of warfare. They took as their habit (the clothes they wear) the white robe with a red cross over the chest. In reality the order was established to "make knights into monks and not monks into knights".
As I stated earlier the book works as a good introduction to the Crusades. Indeed, entire chapters cover much of Crusade history with barely a mention of the Templar. One thing you'll discover is the mendacity of the supposed "nobility" of Europe. The Crusades were hardly a united effort against the Muslims and there seemed to be as many reasons individuals went to fight as there were individuals. Perhaps all of history is like that and its simplified too much in high school history classes.
At any rate the good work of the Templars in protecting pilgrims and the Holy Land from the infidels was richly rewarded by Popes and royalty. The Templars became so rich that they eventually became a sort of multinational banking consortium. After all they had to develop an efficient system of monetary exchange with all the gifts they received. Getting something from England to the Middle East was no easy feat.
As a military force, the Templars were the arch enemies of the Muslims. Even so, the Muslims respected the Templars military prowess and the Templars respected the Muslims fighting abilities. The author richly narrates several military actions and described the knights of the period as the equivalent of the modern-day tank. Despite the power of the Templar Knights they were still only a small force compared to the large armies of the Muslims and Western European kingdoms. Eventually, after about 150 years, the Muslims retake the Holy Land.
The secrecy and supposed riches of the Templars lead many to complain of their avarice. This sentiment was used against them by King Philip IV of France. The early 1300's saw the demise of the Templars by King Philip who accused them of numerous heresies, blasphemies and sodomy. In reality, it appeared that the King had designs on the Templars lands and holdings in France. The King was able to round up 15,000 Templars (knights and associates) in a single day in France. Eventually, many confessed to their crimes under torture, and many died, but on numerous occasions they retracted their confessions when brought before a special commision set up to investigate the charges. After the order was suppressed by the Pope at the Council of Vienne, many surviving members had to join other religious orders.
The author does a good service by providing a chapter at the end on the "verdict of history" on the Templars. He traces how other groups, such a Freemasons, and "historians" have used the Templars for their own end. Indeed, he even mentions the modern day attempt to the co-opt the Templars by prohomosexual groups; they were accused of sodomy after all.
The author's own verdict is that the Templars were, for the most part, made up of "common men". He didn't mean that in a bad way. For the most part they were illiterate and didn't get caught up in some grand vision, but were faithful to their responsibilities. Probably a good word for them would be "average Joes". One final thing that should be noted is that other than landholding and castles there was never found any vast store of wealth among the Templars. Much of the money raised was used to fight the Muslims in the Holy Land (which required an enormous sum). For the most part it appears that the Templars were faithful to their vows of poverty, chastity and obedience.