None so far beside the novelization of the movie by Alan Dean Foster (and the last EU book I've read was a tie-in for TPM that explained how Palpatine manipulated all sides to get elected Chancellor. The big reveal was that he was the one who begged the Chancellor to send the Jedi to negotiate)

They are usually fun, because the novelization writer has access to the director and script writer motives etc. and also to fill gaps. Foster also consulted Rian Johnson who wrote and will direct the next movie. As usual he could also include scenes from the script that were cut from the final edit, usually for pacing reasons. So there's a little more KYlo and Leia in the book, and a scene at the castle that echoed The lost limb at the cantina in ANH and which may have been cut because it was too graphic - it was Chewie who tore an arm from someone who meant to harm Rey. Typically, there's a few extra lines to each conversation, so things are clearer and a bit less like one-liners. Another possible cut scene explained what happened to Poe after the crash and how he found a transport to rejoin the resistance. You also get explanations oddities, such as what Rey was trying to do when she climbed down the wall and entered a kind of pod (she meant to find a way underneath the ramp with the guards to reach the landing area of the tie-fighters to steal one. It didn't work)

That said this novelization is leaner on extra details than the previous ones and some of what's there is also mentioned in interviews with Abrams, like the explanation that R2 got the map to the Jedi temples from the DEath Star archives which he downloaded in ANH. Other than that it's the movie, scene by scene.