Aiden is a gateway, meaning that some dead people need to pass through him - literally - in order to move on. While I'd say this must be challenging enough for a teenager he also needs to prevent a Dark Priest's resurrection.
You get immediately thrown into the action. There very little explanation of what Gateway can or can not do precisely, or more general information on the Gateways. All information that is given to character is usually through the reading of books, even though he has a mentor kind of coaching him who could just as easily tell him these things. It's immediately clear that something is wrong and although I was interested and wanted to know what was happening it still was easy for me to put the book away.
The romance subplot was not too much, but I'd liked to see a bit more of Koren and her history. It is now all thrown in a very exposition-filled scene which, for me, came kind of out of the blue. Not that it didn't sounded interesting, I'd liked to hear more about it, but perhaps not all in the one scene.
I have an ARC also for the second book in the series, so I'll be reading that one shortly.
The Gateway Through Which They Came is the first book in the Gateway series. The second book is The Gateway of Light and Darkness