The Carnac Campaign is a collection of Nightspear, Sky Hunter, and Spirit War.

They're not great. Nightspear at least tries something a bit different in the style of its storytelling. The formatting of the digital edition (or lack of on my devices...) made it difficult to follow though. The print version might be better. Spirit War doesn't actually follow a Wraithknight (let alone an Ulthwe one), contrary to the cover art.

The Path of the Eldar trilogy contains lots of information on Craftworld life and society, but I found the books frustrating. The main characters are unlikable, the plot moves far too quickly (which Thorpe acknowledges in the preface of the omnibus), the climactic battle of the series just sort of happens from nowhere and then ends just as abruptly with a really dumb resolution.

I haven't read them, but Valedor and The Last Days of Ector (and Wraithflight, I assume?) by Guy Haley are apparently very good.

The Dawn of War novels feature Eldar, but I wouldn't advise reading those under any but the most desperate circumstances!