Is The Assassin's Blade Really That Important?

I'm almost halfway through KoA, and I've loved the series like crazy so far. But once I started finding the fandom, I've noticed a lot of ppl talk about Sam and his relationship with Celaena/Aelin. When I started reading the series, I got into like 2 pages of TAB but then gave up bc I had no clue what was happening. Now I'm confused about what order it's supposed to be read in, since I've seen some people say they read it first, and that it was published first, but it didn't seem to be written like it was meant to be read first. I'm really confused about the order now, and I'm worried that I've been missing some important details to understand Celaena/Aelin's character. Should I read this afterwards anyway?