You’re in luck! There’s been a bit of a resurgence in studies of the crusader states lately. And there are still lots of good old books too.

For the crusader states in general:

- Andrew Jotischky, Crusading and the Crusader States (Routledge, 2013)

- Malcolm Barber, The Crusader States (Yale University Press, 2012)

Those two are pretty reader-friendly. An older book, a bit more specialized about the crusader church, but still enjoyable, is:

- Bernard Hamilton, The Latin Church in the Crusader States (1980)

For the Kingdom of Jerusalem, the biggest and most important of the crusader states, a lot of the books are much more specialized…is there a basic introduction to the KoJ? Not really. I wouldn’t really say most of these are for casual readers, but if you’re looking to go into deeper detail, see:

- Joshua Prawer, Crusader Institutions (Oxford University Press, 1980, repr. Sandpiper Books, 1998) - here Prawer talks about the development of the legal structures of the Kingdom of Jerusalem. It's pretty hardcore.

- Joshua Prawer, The Crusaders' Kingdom: European Colonialism in the Middle Ages (Prager, 1972, repr. Phoenix Press, 2001) - this one is a bit more accessible, but Prawer's assertion that Jerusalem was an early kind of colonial state has not really been accepted by most historians. Still, a pretty fascinating read (but very long!).

- Jonathan Riley-Smith, The Feudal Nobility and the Kingdom of Jerusalem, 1174-1277 (Macmillan, 1973) - like Prawer's Crusader Institutions, this is more about administration and bureaucracy, lots of deep nitty-gritty details.

- Ronnie Ellenblum, Frankish Rural Settlement in the Latin Kingdom of Jerusalem (Cambridge University Press, 1998) - also about colonialism, in a sense, but Ellenblum argues that the crusaders for the most part lived separately from the Muslims and adopted the living patterns of the Christians who had always lived there before them.

- Yvonne Friedman, Encounter Between Enemies: Captivity and Ransom in the Latin Kingdom of Jerusalem (Brill, 2002) - one aspect of life in the crusader kingdom, how both sides dealt with prisoners and slaves.

And two classic books about warfare in the crusader states:

- Christopher Marshall, Warfare in the Latin East, 1192-1291 (Cambridge University Press, 1992)

- R. C. Smail, Crusading Warfare, 1097-1193 (Cambridge University Press, 1956, 2nd ed., 1995)

For the other major crusader kingdom, on Cyprus:

- Peter W. Edbury, The Kingdom of Cyprus and the Crusades, 1191-1374, (Cambridge University Press, 1993)

- Nicholas Coureas, The Latin Church in Cyprus, 1195-1312 (Routledge, 1997)

For Antioch:

- Thomas Asbridge, The Creation of the Principality of Antioch (Boydell, 2000)

- Andrew D. Buck, The Principality of Antioch and Its Frontiers in the Twelfth Century (Boydell, 2017)

And for Tripoli:

- Kevin James Lewis, The Counts of Tripoli and Lebanon in the Twelfth Century (Routledge, 2017)

I don’t know of anything recent about the County of Edessa, unfortunately.

Thanks so much! Looks like I’ve a lot to read!!

Sorry about not directly responding to your comment I’m still super sleepy.