I just finished binge-reading the 'Throne of Glass' series, and figuring out the order was a bit tricky at first. The best way to dive in is to start with the original 'Throne of Glass' novel. It introduces Celaena Sardothien, the assassin with a heart of gold, and sets the stage for everything that follows. After that, move on to 'Crown of Midnight' and 'Heir of Fire' to see her journey unfold.
Next, read 'Queen of Shadows' and 'Empire of Storms' back-to-back because the stakes get higher, and the lore deepens. 'Tower of Dawn' is a parallel story to 'Empire of Storms,' focusing on Chaol and Nesryn, so you can read it after or alongside. Finally, cap it off with 'Kingdom of Ash,' the epic conclusion that ties everything together. If you want extra backstory, 'The Assassin’s Blade,' a prequel collection of novellas, can be read either before the series or after 'Heir of Fire' for maximum emotional impact.