Okay I just finished re reading OOTD and Into the Light, prefatory to the new To Challenge Heaven. I'm several chapters into the new one. It is totally AWESOME! I ofc have no idea where it's going or how it ends but....what I have read so far is awesome.
David (as you should already know) has a thing for homo sapiens surprising "advanced" alien races with our astounding technological prowess. Think about his stand alone story of The Excaliber Alternative, the trilogy of the Dahak story and ofc OOTD AND ITL. Well, To Challenge Heaven are those six books on steroids. I HIGHLY recommend re reading the first two of the OOTD books and running out to buy the third. I'm not sure if it will get any better as it goes along, I KNOW that there's NO WAY it will be worse.
I will post again when I finish, and don't worry, there's no way I'll give any spoilers. It's too good to do that. I wouldn't think of doing that!