Most of them have been mentioned in this thread, but they did a cool thing when Disney started publishing the new canon paperbacks. All the old EU stuff that doesn't count now says Legends right on the spines of the books, and the canon books are all about a half inch taller than all the old stuff, so they really stand out on the shelves. I'd definitely start with Lost Stars, Aftermath isn't great at all but it's going to be a trilogy ending with more battle of Jakku stuff so it's probably relatively important, and I really enjoyed Dark Disciple, the Asajj Ventriss book, which also establishes some Jedi abilities that already have shown up in TFA.