I’d hesitate to call it an absolute monarchy because they do seem somewhat constrained by law or tradition, but I’m not aware of any formal process by which either the nobles or the commoners (I don’t believe there is any Parliament) can officially exert any authority.

I believe it’s based on a mediaeval English or French monarchy.

The closest non-D&D fantasy kingdom I can think of would by Andor in Robert Jordan’s Wheel of Time series, except that there is a very clear very strict line of succession instead of Andor’s nobles essentially voting on a successor.

Book 4 of Erin M. Evans’ excellent Brimstone Angels series is set in Cormyr and deals extensively with its politics, and I would highly recommend that book to anyone interested in that sort of political intrigue.