There are 90 collectibles throughout the 8 levels - I have all of the collectibles in each video to make this easier for you to follow. It is possible to get videos using the Smartglass Companion app, You are welcome to do this, But it is pretty confusing. It is only available on tablet too which is pretty poor.
Here you can also track how many you have to collect - But following these videos should take the hassle out of it for you.As soon as you collect the collectible it saves which is great too!
Chapter 1 : The BeginningChapter 2 : S.P.Q.RChapter 3 : Trial By FireChapter 4 : The KingChapter 5 : Edge Of The WorldChapter 6 : Pax RomanaChapter 7 : The Wrath Of NemesisChapter 8 - Son Of Rome