General assessment? It's pretty good. I like it a lot. It has mistakes, but nothing so glaring within a context of a classic film that makes it unwatchable. The truth is, of course, more interesting, but it's a lovely film.

David Lean's "Lawrence of Arabia" is primarily based off of Lawrence's memoir Seven Pillars of Wisdom. In its depiction of Lawrence it captures I think a lot of the essential issues of the man: his unsuitability for the military, his intellectuality, his effeteness, his sympathy for the Arab cause.

Lean's film does, however, fictionalize quite a lot for the stake of story arc. Lawrence was not some unimportant schmo in a map room in Cairo. His military commission was the direct result of his knowledge about the region. While in London he was supposed to give a military briefing and was informed that he wouldn't be allowed into the briefing unless he, too, was in uniform. So, he was duly sent out to a uniform shop, told to buy a lieutenants uniform and was given a commission. Upon arrival in Cairo he was a favorite of the Egypt intelligence establishment that was virtually responsible for the entire war planning effort. There's some debate about precisely how much he knew, but on issues like the Hussein-McMahon correspondence and the Sykes-Picot agreement, it's widely assumed that he must have known quite a lot before he even went to Arabia.

Some of the key plot points of the film also get things precisely backwards. General Murray's line that an Arab revolt would be a "sideshow of a sideshow" is actually a quote from Lawrence himself. His view of artillery that is expressed in the movie is a bit different in the books. He wanted Faisals army to have mobile artillery but not heavy field artillery.

Part of the inaccurateness of the film is the result of Lawrence's own falsities in his book. His supposed capture and torture by the Turks is one such widely disputed story. I don't actually have a strong opinion on the matter myself, though many claim that Lawrence entirely fabricated the incident as part of his own (homo) sexual proclivities. The scope of the film is affected by this as well. The movie (and his book) make it seem as though Lawrence's involvement and responsibility ended the moment the Arabs reached Damascus. It did not. Lawrence remained intimately involved in the wartime settlement for years after the fall of Damascus. He was a primary participant in the [Paris peace conference in 1919.] (https://www.cliohistory.org/fileadmin/processed/c/d/csm_2_Paris_f785af5067.jpg) (He was Faisal's "translator". Supposedly, he wrote the English speech while Faisal recited the Quran at the podium, knowing that no other attendees spoke Arabic and that it would sound impressive.) He continued in his role as Middle East expert par excellence at the Cairo Conference in 1921 which ultimately resulted in the formation of Jordan as a Hashemite state and the creation of Iraq with Faisal as King.

There's also I think something to be said about Lawrence's depiction as a military figure in the film. While they're included, I think the film downplays the technical expertise provided by NCOs and other British figures in simply training the Arab army in the ways of guerrilla warfare. I think it's also worth noting that the revelation that Lawrence was leading the Arab army was, at first, entirely unintentional. It was first revealed by French journalists trying to discredit British efforts in the region until the revelation itself made Lawrence something of a celebrity.

I think also in making a character, though he downplayed some of this himself, you lose quite a lot of Lawrence as a man. You miss out, for example, on the fact that Lawrence lost two of his brothers on the Western Front. Lawrence himself seems to downplay this in his letters, and we shouldn't regard him as unusual within the context of WWI, but that's nonetheless quite a burden to bear.

Lawrence's background is elided in the film generally. Virtually the entire rationale for his rank and position was that he had served on an archaeological dig in Syria (i.e. Greater Syria, including Jordan/Palestine, the dig itself was near the modern Turkish border at Karkamis) before the war and had viewed the entire region on foot as part of his university dissertation. The scene in which he eats and is surprised by Bedouin food, while as far as I'm aware it might have been his first time in the Hejaz, must have been a fabrication insofar as Arabic food is frankly not all that diverse. I haven't confirmed this but it's also my understanding that his knowledge of Arabic was pretty mediocre.

If you have any questions about any specific aspects of the movie I'd be happy to address them as best I can. As I said, it should be remembered at all times that it's fiction, but it's too good a movie to ignore and I think is truthful to the man in many ways. Sourcewise, Lawrence's own Seven Pillars of Wisdom, Scott Anderson's Lawrence in Arabia, and I'm currently reading parts of Lawrence's authorized biography, though I'm nowhere near finishing it. Other than that, lots of books that touch on Lawrence tangentially.

Edit: I could nitpick quite a lot more, I don't mean for this post to be exhaustive. For example, in his memoir Lawrence makes clear that he selected Faisal among Sharif Hussein's sons, whereas in the film we never meet the other sons. The film also involves multiple composite characters, perhaps most notably Dryden. I could go on. If anyone wants to know more about specific issues I can try to answer those, I've mostly focused on broad impression topics.

Edit 2: looks like I know what I'm watching tonight.

Edit 3: This site seems to include a scene-by-scene debunking. I agree with it as scene-by-scene criticism, but my overall assessment that "Hey, it captures the man pretty well", stands for the reasons I've explained. As I said, its a horrifically "inaccurate" film; that's somewhat beside the point.