Awesome thanks! I will have a look at your suggestions. I just realised today that The Core is new so I've bought that on kindle and I need to refresh my memory on the last book that came before it (The Skull Throne?) as I read it a few years ago now.
The Forgotten is actually sci fi but I found it pretty interesting, there are only two books so far its by M.R. Forbes.
If you haven't read Outlander you're in for a treat, lucky you!