I have finished the main part of the Dawnguard DLC but I can't start the Lost to the Ages quest. I've read the book "The Aetherium Wars" and nothing happened. I checked the misc section in my journal but there's nothing there to do with the quest. Am I missing something?
Reading the book 'The Aetherium Wars' will initially only trigger a miscellaneous quest in which you have to 'Investigate the ruins of Arkngthamz':
There you will meet Katria, and this will trigger the 'Lost to the Ages' quest.
As user Roddy of the Frozen Peas suggested, there are other methods to get the quest 'Lost to the Ages' started.
Apart from reading the book 'The Aetherium Wars', you can
- travel to Arkngthamz, or;
- find any one of the four Aetherium shards (at that point called 'Glowing Crystal
Arkngthamz can be found south-east of Markarth:
One of the four Aetherium shards can be found there as well, and the other three are in
Another possible explanation is that you encountered a bug that prevents you from properly starting the quest even if the requirements are met.
There are two bugs mentioned on the UESP quest page that your playthrough might have been affected by:
Reading The Aetherium Wars may not add the miscellaneous objective "Investigate Arkngthamz" to your quest log. Upon investigating Arkngthamz, "Lost to the Ages" may not be added to quest log, either, meaning that you will be unable to complete the quest.
A way to fix [this] is to reload a save in which you have not started the Dawnguard questline, then drop The Aetherium Wars and any crystal shards if you have obtained any, and pick the book back up and read it. The quest should start, and then you can pick up the shards.
This quest may not start if, after installing Dawnguard, you have visited Mzulft or Deep Folk Crossing prior to reading The Aetherium Wars and the corpses at these locations have been fully removed from the game.
This bug is fixed by version 2.0.1 of the Unofficial Dawnguard Patch [now part of the Unofficial Skyrim Legendary Edition Patch].