The game Total War: Rome II has it as a faction and it got my attention. I've been going through the Wikipedia pages reading a little about the dynasties, the wars and battles against other civilizations, army composition...
Maybe I don't know how to search properly but I haven't found as much information as I was hoping to so any book recommendation or any other source to go deeper would be highly appreciated.
Besides from the already mentioned and very useful "The Land of the Elephant Kings" of Kosmin, I'd like to add some more things:
Although it's somewhat outdated nowadays (its last edition was made around 1965), there is a two volume history of the kingdom called "The House of Seleucus", written by Bevan, which still works pretty well for a general introduction of the empire's political evolution, the reason being that serious studies on the Seleucid Empire were almost non existant for decades since this book was piblished.
However, the most modern and updated recommendations I can think of are Sherwin-White and Khurt's From Samarkhand to Sardis, which doesn't really cover the history of the empire, instead discussing the very nature of it and debating some consolidated ideas of the kingdom, such as that of "continual decadence" inherited from the roman sources.
For political developement of the kingdom, there's a very new three-volume history witten by John Grainger, who divides the developement of the empire in three stages, one for each book: "The Rise of the Seleukid Empire", from the death of Alexander the Great in 323 to that of Seleucus III in 223; "The Seleucid Empire of Antiochus III", from 223 to 187, undoubtedly, the best recorded period of seleucid history, and "The Fall of the Seleucid Empire", from 187, the date of Antiochus III's death, to the creation by Pompey of the roman province of Syria.
Lastly, if you're interested in some more particular matters, Grainger also has written a biography on Seleucus I, "Seleucus I, Constructing a Hellenistic Kingdom", and "The Cities of Seleukid Syria", studying how the seleucid monarchs turned Syria from a rural area to the densely -for Antiquity standards- populated, prosperous and urbanized region it became. I'd mention also Michael Taylor's "Antiochus the Great", a biography of the seleucid king we know the most of, basically, because of his war with Rome, Bar-Kochva's "The Seleucid Army", an in-depth study, as much as our scarce sources allow us, of the kingdom's military, and also Aperghis' "The Seleukid Royal Economy" which I haven't yet read, but I know to be worth doing so.
Hope it's enough!
Land of the Elephant Kings by Peter J Kosmin. I read it a couple months ago. It mainly goes over how it was governed, how the polis system functioned, the economy etc. It doesn't really go into the rulers themselves but it's pretty informative in my opinion.