Thomas Asbridge’s The Crusades: The Authoritative History of the War for the Holy Land is a very readable account of the Crusades, from the surprising European success of the first one through all the twists along the way, ending with (spoilers!) Europeans finally being evicted from the Crusader kingdoms, and including a cameo from special guest star Genghis Khan.
Asbridge does an excellent job contextualizing the Crusades; a key thing about them is that they nearly always represented foreign policy for the various European and Islamic polities, and foreign policy is rarely as compelling to a populace as domestic concerns are, so very little of the Crusades make any sense without understanding what was going on beyond them; and then of course, foreign policy concerns inter-relate to each other in ways that are not just as simple as “Europe vs. Islam”, and Asbridge explains why a Pope would excommunicate a successful Crusading king, why the Islamic ruler of Egypt would be unwilling to send help to Syria, why a holy mission for Jerusalem would instead sack Constantinople.
The other thing Asbridge does well is in relating the history from the perspective (and sources) of both the Islamic and European worlds, so you can get a picture of how events were seen both to the Crusading Europeans and to the Muslims who fought against the invading armies. Saladin, for instance, is seen not just as a steadfast opponent of the Crusaders, but as a figure whose dynastic ambitions put him in conflict with other Islamic rulers, and who had to deal with a great deal of politics and conflict in establishing the Ayyubid dynasty.
This is mostly a straightforward narrative history—it doesn’t feel sensationalistic or overly “popular,” but it’s certainly no dense academic thicket—that follows events and people over the course of centuries, but the conclusion does have a short historiography of the Crusades which talks about the ways in which they’ve been seen over the centuries (and, of late, used by propagandists).
The book isn’t so well-written or so revelatory that it rises to the level of a must-read, but if you’re interested in the topic, it’s a solid overview without any obviously glaring flaws. Recommended.