I started reading the Aftermath books after watching TFA because I really wanted to like the movie more. I bought all three after Rogue One. … I can now say those books are terrible! I held my nose through a book and a half before I saw the TLJ. I am done.
For the record, the Aftermath trilogy won’t do shit to help you understand the context of the sequel trilogy. Claudia Gray’s Bloodline is what you’re looking for.
I will give it a shot. I am really thinking about finally reading that Thrawn series.