Tangential to your request, I would highly recommend as a prologue/historical fabric, Dalrymple's "Return of a King." A non fiction account of the first invasion of Afghanistan by the British circa 1839.
In the events that unfold, you can see precursors to the modern conflict, generally from the lack of understanding the great discrepancies of Afgani and western cultures. Link below:
https://www.amazon.com/Return-King-Battle-Afghanistan-1839-42/dp/0307948536
Whatever modern book you end with (or not), consider this one as well.
I remember skimming through Return of a King at a bookstore and there was a part where the ruling Sikhs are holding a prince hostage in his own palace and this prince referring to the Sikh's as "barbarians". It's rare that an occupying force or its leader is looked upon favourably by the occupied people.
Basically what it boils down to is a lack of compatibility with democracy, as I already noted. Throughout Afghan history, there has been no concept of a greater state except in times of foreign intervention. Democracy relies on the concept of a nation-state to bind its people together. The US and NATO at large tends to rely on western-educated leadership that they utilize as puppets -- which is their downfall. Here's a good wikipedia article and book to read about what happens to puppets in Afghanistan:
https://www.amazon.com/Return-King-Battle-Afghanistan-1839-42/dp/0307948536
https://en.wikipedia.org/wiki/1842_retreat_from_Kabul
Afghan forces essentially had enough of the puppet in Kabul at the time and deposed him.
Afghanistan requires -- in my opinion -- three major attributes in a leadership.
1.) A heavy hand
Strongmen are the only forms of leadership that have shown any sort of possibility of maintaining a stable and effective level of governance in Afghanistan since the modern state's founding in 1747. Great examples of such strongmen are Abdur Rahman Khan (r.1880-1901) and Atta Mohammad Nur (r. Balkh Province, 2003-present). Studies on security in Afghanistan have shown that the most secure provinces are those who are considered "warlords" by the west. Those who are western educated or longtime Afghan ex-pats who returned in 2001 are generally far more in effective, which brings me to my next point.
2.) Strong internal connections
Provincial governors -- and national governors before them -- that have had strong internal family and tribal connections have had the most success in security and stability within their provinces. Two good examples: Dost Mohammad Khan (r. 1826-1863) and Gul Agha Sherzai (Governor of Nangarhar under Karzai).
Dost Mohammad Khan and his son Wazir Akhbar Khan were able to outmaneuver the British-backed Shah Shuja (who had been in India for some 10 years after the rise of the Dost) due to their deep, deep patronage networks. These internal networks are still alive and well today and are part of the reason Karzai was so effective in the early years of his reign.
Gul Agha Sherzai is what one could call an "outsider" governor in Nangarhar in that he was a Kandahari that was placed in his post by Karzai to avoid tribal warfare between the Sherzai and the Karzai. Sherzai immediately worked to create his own deep-reaching networks in Nangarhar to stabilize the province, and did so quite effectively.
3.) An above-average understanding of foreign politics without being beholden to a foreign power
As a kind of alluded to at the beginning, it is necessary that Afghan leadership understand the world stage without being beholden to a foreign power (see: Zahir Shah). Without the former, a government will be unstable because world actors will see them as unpredictable. In the mid 1970s, Daud Khan (cousin of Zahir Shah) attempted to really push the Pashtunistan issue with Pakistan in an effort to get them to turn over Pashtunistan to Afghanistan. This resulted in the ISI's clandestine funding of Islamist groups in Afghanistan such as Jamiat-e-Islami and Hezb-i-Islami (Gulbuddhin Hekmatyar's group) that culminated in an attempted revolt in 1975 that did weaken Daud's hold on power.
If a government is beholden to foreigners, it becomes easy for hostile internal actors to make the argument that they are puppets of a colonial power, such as the Dost did to Shah Shuja in the 1840s, or the Mujahideen to Najibullah and Babrak Kamal in the 1980s, or Ashraf Ghani today.
So I suppose my point is that the US wants a democratic government run by pro-US leadership that is going to do their bidding, but that just isn't going to work longterm, and democracy is not compatible in Afghanistan.
Now, will strongmen by the answer for a forever peaceful Afghanistan without internal strife? I don't know, frankly, but it seems that on a small scale it works -- but it all requires one charismatic guy to bring the entire country to heel. It will definitely be interesting to see what happens in the next elections in AFG -- if they happen at all.
This is behind a paywall but this is the source for the study on strongmen: http://as.ucpress.edu/content/55/2/299
"What happened next is a warning of how bad things could yet become: a full-scale rebellion against the British broke out in Kabul, and the two most senior British envoys were murdered, making the British occupation impossible to sustain. On the disastrous retreat that followed, as many as 18,000 East India Company troops and maybe half again as many Indian camp followers (estimates vary), were slaughtered by Afghan marksmen waiting in ambush amid the snow drifts and high passes, shot down as they trudged through the icy depths of the Afghan winter.
The last 50 or so survivors made their final stand at Gandamak. As late as the 1970s, fragments of Victorian weaponry could be found lying in the screes..."
Return of a King: The Battle for Afghanistan, 1839-42...great book about the British learning their lesson about fighting in Afghanistan.
I can't think of any modern army that's ever conquered Afghanistan.
Hahaha this book, if anyone bothers to read it, will tell you what a colossal failure that was. https://www.amazon.com/Return-King-Battle-Afghanistan-1839-42/dp/0307948536