The word that best describes the mood of the letter's writer might be "beleaguered." He laments the recent loss of a wife, son, and daughter, for one thing. He hints at money problems and asks for cash, for another. He complains that not all of his recent works have been published, and that he's lost the manuscript of his last book. He notes, parenthetically, that American Intelligence has apparently acquired his computer.
Some experts suspect that the letter is a fake, and that the CIA - not Al Qaeda bigwig Ayman al-Zawahiri - may be its true author. It was US Intelligence that made public the 13-page missive, after all.
Others call it a fascinating document, and say much of it rings true. Take the letter's description of Al Qaeda's ultimate victory, in which the US is expelled from Iraq, Israel is conquered, and all Muslims - including Shiites - are converted to an extremist version of Sunni Puritianism. That's long been the terror group's bleak vision for the future.
"If [Zawahiri] didn't write it, it was certainly someone who understands what Al Qaeda wants," says retired Brig. Gen. Russell Howard, a counterterrorism expert at the Fletcher School at Tufts University.
Posted in full last week on a US government website, the 6,000-word letter is purportedly from Ayman al-Zawahiri, Osama bin Laden's deputy in the Al Qaeda organization, to Abu Musab al-Zarqawi, Al Qaeda's top man in Iraq.
Mr. Zarqawi and his group of Islamist insurgents are thought to be behind many of the most deadly attacks in Iraq, including suicide bombs directed at government targets and Shiite civilians. In the letter, Zawahiri thanks Zarqawi for his efforts, and says that Iraq "is now the place for the greatest battle of Islam in this era." Other Islamist conflicts, such as those in Afghanistan and Chechnya, are just "groundwork."
Mr. Zawahiri then outlines what he calls Al Qaeda's incremental goals for the future. First, expel the Americans from Iraq. Second, establish an Islamic authority, or emirate, over as much Iraqi territory as possible - "i.e. in Sunni areas" - to fill the vacuum left by the departing US power.
The third stage involves extending this wave of jihad to the "secular countries neighboring Iraq." Then, according to the letter, comes a final confrontation with Israel, "because Israel was established only to challenge any new Islamic entity," and establishment of a regional caliphate in which other sects of Islam convert to Al Qaeda principles.
Zarqawi and his jihadist forces need to be ready to implement this strategy because "things may develop faster than we imagine," says Zawahiri in the letter, citing the US experience in Vietnam.
Then the admonitions begin. Beheadings of hostages, and suicide attacks against ordinary Shiites, are not helping the movement, Zawahiri warns. The Muslim masses are put off by such slaughter. Even the elite of the mujahadeen may question the correctness of picking a fight with the Shiites "at this time."
The bottom line is that popular support may be the difference between victory or defeat. "We are in a battle, and ... more than half of this battle is taking place in the battlefield of the media," says the letter.
Last Thursday, Al Qaeda's wing in Iraq denounced the document as a fake. In the US, some experts noted its convenient release date, just prior to Saturday's Iraqi constitutional vote, and the fact that the English translation of the text did not contain many of the flowery religious asides that have characterized Al Qaeda communications in the past.
The blessing on the prophet Muhammad invoked at the letter's beginning doesn't sound right, according to Juan Cole University of Michigan Middle East expert. He claims it appears to reflect Shiite, not Sunni, language.
"My gut tells me the letter is a forgery," Mr. Cole wrote Friday on his popular Middle East website, adding that Shiite groups in Iraq may have produced it.
The US government, for its part, has vehemently defended the missive's authenticity.
"It shows clearly the nature of the enemy we're dealing with," says State Department spokesman Adam Ereli.
Other experts say the letter's contents should not seem too surprising. It's true that serious splits in the jihadist movement have emerged in recent months, centering on the war in Iraq and Zarqawi's use of suicide bombings, says Bernard Haykel, an associate professor of Islamic studies at New York University.
He says it's easy to find evidence on jihadist websites and online journals that Zarqawi's attacks on ordinary Shiites in Iraq are turning many Muslims against the jihadists altogether.
It's possible the attacks "are making them lose credibility with their support base," says Mr. Haykel.
The issue for the jihadists may well be a practical one - possible loss of support in the region - rather than respect for Shiite religious rights.
In Iraq, the most extreme of the insurgents, such as the Al Qaeda contingent led by Zarqawi, see their current activities as part of a broader struggle for an Islam dominated by their narrow view of Sunni Puritanism, writes Anthony Cordesman, a military expert at the Center for Strategic and International Studies.
The question is not whether there will be a struggle against Shiites, but when.
"Such insurgents do not have to 'win' in Iraq, at least in any conventional sense of the term," writes Mr. Cordesman in his latest report on insurgent patterns. "An outcome that leaves Iraq in a state of prolonged civil war, and forces a spreading conflict in Islam between Sunnis and other sects ..., would be seen as a prelude to a broader eschatological conflict they believe is inevitable and that God will ensure they win."