The Kyoshi novels are darker, more mature and more lore dense than the comics. Would recommend.

I still need to read the Yangchen books myself.

I did not like the comics nearly as much as the shows, but YMMV.

And hear me out… but the top 0.1% of Avatar fanfiction is quite something. Easily the next best thing after the 7 original Books/seasons.

As a side note, multiple of the comics have been slightly animated by fan projects and are available on youtube.

I think all of the ATLA comics are solid, especially the ones illustrated by Gurihiru (but then again I absolutely love Gurihiru’s style so I’m totally biased). Some aspects are a bit weird (like the forklift in The Rift) but the comics match the tone of the show fairly well.

A particular mention should go to one from the Lost Adventures, the one about Private Wang Fire. A true Fire Nation hero!