Beyond learning more detail about the dysfunctional tribalism of a country whose current, colonial-imposed borders make even less sense than most of those in Africa (either western Pakistan and its Pashtuns should be added to Afghanistan or southern Afghanistan and its Pashtuns should be added to Pakistan, for starters) the single biggest takeaway I got from this book?
The HUGE degree of outright lying, and other general deception, practiced by Pakistan's Inter-Services Intelligence, the infamous ISI, to its own country's (and its own institutional) goals, often shortsighted ones, since even before the old USSR officially announced it was pulling out of Afghanistan.
Pakistan's long-term President Zia, per the author, said that in negotiations it was perfectly OK to lie to the USSR since it had non-Muslim leadership. It's clear from this book that he and many other Pakistani leaders must feel the same about the United States. (That said, they at least indirectly lied to the Saudis at times, too.)
That said, speaking of Zia, Pakistani heads of government, including but not limited to Zia, and both civilian and military in background, have shown plenty of their own duplicity.
Second biggest takeaway? Long before 9/11, the CIA was clueless about A-stan, and what it called "intelligence" was usually stuff uncritically culled from the ISI. Too bad we didn't have leadership after 9/11 who saw this as the perfect reason, time, and excuse to get rid of the CIA.
Thomson was the first U.S. representative to Afghanistan after the Soviets announced their pullout, with ambassadorial rank. He repeatedly saw firsthand both ISI duplicity and CIA ineptitude (mixed with undercutting the State Department; that happened more than the ineptitude during his 1989-92 service).
Given that the ISI is still in true control of Pakistan, and given that it will go to any end for its own objectives (including, as events of this spring showed, some likely complicity in harboring bin Laden), why are we still in Afghanistan? Short of actual full-blown war with Pakistan (or siccing India into that), and not just pinprick drone attacks, nothing we do will change its course, period.
And, as Thomson details the degree of dysfunctional tribalism, if we stay, anyway ... what do we expect to accomplish?
That said, there are some errors, mainly minor, in the book. "Millennia" is a plural word, not a singular, for example.
But, this book is still chock-full of information on Afghanistan of the past 100 years, and well worth a read.