On motivations, grievances, etc., in the case of bin Laden I don't know of anything that goes beyond the standard sources: Jason Burke's al-Qaeda, to mention the best I know. Roughly the same in Scheuer's Imperial Hubris, Randall's Osama, and others, who give more or less similar analyses. Most take bin Laden pretty much at his word. The Pentagon apparently agrees as well. Wolfowitz explained reduction of US military forces in Saudi Arabia as a means to reduce the declared motivation that terror against the US is a reaction to US occupation of SA. In the case of bin Laden it is generally assumed to be the general ideology he has articulated over the years: in his terms, defense of Muslim lands from infidel occupiers and aggressors, overthrow of the corrupt rulers and imposition of his version of purist Islam. I don't have any independent evidence beyond the (largely shared) standard analyses.
Grievances are a different matter. Bin Laden-style terrorists apparently perceive themselves as a vanguard, seeking to mobilize others who may dislike and even fear them, but recognize that there is some justice in the cause they profess. As to these grievances, they've been no secret at least since 1958, when Eisenhower raised questions about the "campaign of hatred against us" among the people in the Arab world, and the National Security Council attributed it to their perception that the US supports brutal and corrupt dictators and blocks democracy and development because of its interest in controlling the oil resources of the region. Later investigations, intensifying after 9-11, found essentially the same results, along with anger about specific policies, particularly US support for the brutal Israeli occupation of the conquered territories and the murderous sanctions that were devastating the civilian population of Iraq. These grievances have only, of course, extended since the invasion. I doubt that you'll find much disagreement about this among specialists and intelligence agencies.
Of course, dogmatic ideologists prefer to orate about how they hate our freedoms, want to drive the Jews into the sea, etc. But I don't think serious analysts pay attention to these declarations.
How you evaluate the motivations is, of course, up to you.