The delayed answer to the many questions posted by fans herein, is that the original author is named Rick Yancey. Both he, & the guest authors which are posted under the @5thWaveMovie account, became inactive some time after the movie premiered in theaters. The original book, as well as these guest authored novellas written exclusively for the movie promotion, are all excellent stories. Available here on Wattpad (abandoned after the movie).
The 2nd main book is on Wattpad under Rick Yancey's account name, but abandoned without further notice by the original author. This may be due to the heavy criticism of the movie, storyline, and faulty reimagining of the movie's Directors. The same Directors that seriously botched the vision of the book written by Yancey.
If I was the writer of such a grand vision, one that was HEAVILY hyped all across the internet for the year running up to release, and having it flop because some idiot Directors could not shoot my vision (even with my advice)...I would probably take a similar hiatus from that same internet as well. No joke.
Then again, Yancey has thousands++ of fans just from the stories alone. This Wattpad account was mainly for promotional purposes, so author replies are not likely to happen. It was crushing to all of us that the cuts made by the Directors really chopped up the original storyline too much to effectively pass Reviewer (and fan) critique.
Personally, I liked the movie only because I had read the original + novellas here on Wattpad first, and was proud that Yancey had a chance to showcase such a wonderfully fresh variation of the alien invasion theme on the big screen. If I had seen the movie first, I would have thought it had more of a made-for-TV feel to it. Again, the fault of the Directors. Enjoy this humble review, and the stories linked to The 5th Wave. :)
(Missed the movie-linked guest authored novellas? Hop over to the @5thWaveMovie account here on Wattpad!)