So I was just gonna put this info in a comment but I want to make sure everyone sees this. So if you didn’t already know each class, mage, rogue, and warrior, has 3 specializations. You can unlock these specializations once you get to Skyhold and are level 10. Go to your war table and on the Ferelden side find the quest that’s called Specialists for the Inquisitor (or something similar to that).
This unlocks three people that will then appear in Skyhold and each one offers a quest for a different specialization. I suggest you do a little research before choosing as you cannot choose again. Each specialization has a quest line and each quest line you have to get a book and other items for. Most of the books are sold in Val Royeoux (I know I spelled it wrong but too lazy to look up the real spelling) however some you can find next to or by talking to your companions that are that class. Hope this helps.