"Xenocide" by Orson Scott Card

This is the third book in the "Ender Tetralogy", which was the original envisioning of the series (which got much expanded afterwards and pretty much turned into a franchise).  The original envisioning was a trilogy actually, "Xenocide" and the following book "Children of the Mind" supposing to be one volume, but it became too lengthy for one book, so it got split into two.  "Xenocide" is the only Ender Tetralogy book where the story doesn't end naturally on the last page, but actually ends in mid-action.  "Xenocide" is a very ambitious book, almost like a space opera of the likes of Dan Simmons or Ron Hubbard.  There are multiple settings (on two planets) stories, plots, twists, etc.

The Starway Congress fleet is advancing towards Lusitania with the MDD device on-board, while Ender is trying to get the piggies (pecaninos) and the hive queen off the planet before Jane is turned off for the most part.  A genetically enhanced, but OCD_controlled humans on the planet called Path are much more intelligent than normal humans, and are used by Congress to advance their aims.  Path is populated by Chinese, and lives in a very traditional, patriarchal, class society.  Meanwhile on Lusitania, human scientists are trying to develop a form of the Descolada which will give Pecaninos their life processes, but will not be aggressive and harmless to humans.  They call this new virus the "Recolada" but it only gets created during the first faster-than-light experimental trip.

Eventually Jane with the help of Ender, Grego and some insights from the Hive Queen finds a way how to travel faster than light and pretty much instantenously to anywhere in the universe. However, as a consequence of the first trip, Peter and Valentine, as they were in Ender's mind were created in flesh and blood.  The book ends with Peter bringing a virus that will cure the people of Path of their OCD.  The solution to all plots is in the next and final book of the "Ender Tetralogy" - "Children of the Mind".