Whenever I'm immersed in studying a particular piece of history, it always seems to be of monumental importance and world-shattering impact. It's a little bit of a shock to hear someone discount it as boring, irrelevant, or not worth their time.
No, I'm not talking about reviewers. I'm talking about historians, and dead historians, at that. I've heard second-hand that most medieval Muslim historians didn't even mention the First Crusade since it was too insignificant to be worth their time.
My most recent research reading is The History of the Seljuq Turks: The Saljuq-nama of Zahir al-Din Nishpuri a translation of a twelfth-century Muslim history which I obtained through interlibrary loan. I sped through the founding of the Seljuk empire and was on the edge of my seat to get to the reign of Sultan Barkyaruq, the man who reigned during the Western invasion of the Holy Land. When I got there, I discovered that the reports I'd heard were correct: the Crusaders were not even mentioned.
The closest thing that could be a reference to the Crusade was the introduction to Barkyaruq's reign:
"In his time there occurred many difficult events, unpleasant happenings, upheavals and much agitation." Of course, this sentence could also be referring to the internecine struggles which plagued his reign as he fought a war of succession with the sons of his father's other wives.
When historians are silent about a subject, it's easy to put your own interpretation on the reason. In this case, the standard interpretation is "the Crusade wasn't important enough to be mentioned." In an empire that stretched from Asia Minor, through Iraq, through Persia, and all the way to India, it is plausible that happenings on the coast of the Mediterranean might be of minor importance compared to battles between brothers in Baghdad or Khorosan.
And yet, in other places of the work, the historian shows that he is not ignorant or indifferent to the Mediterranean area of the world. The chapters discussing the reigns of previous sultans jubilantly recount the Turkish conquest of Christian Asia Minor--a large part of which the Westerners recaptured in the First Crusade. The historian is very interested in the Turks' interactions with Byzantium, especially the part where Alp Arslan crushed the Eastern Roman Emperor at the Battle of Manzikert. Why then is he not interested in the Byzantine counter-offensive (as the Crusaders were often considered, since they had been called to the East by Emperor Alexios)?
Perhaps one reason that the medieval Muslim historians do not like to mention the First Crusade is because it is primarily a story of Muslim failure. It is a story of a ragtag band of Western knights who overcame tremendous odds to free the Holy Sepulcher and carve out five kingdoms in the Middle East. Perhaps it's not so much that the Crusade held too little significance, but that its significance was too tremendous and too terrible to be mentioned. Perhaps my argument from silence is as plausible as the current interpretation.