Rules for unlocking tomes?

[Alterum]

Are the rules clear to anyone? Initially, I had thought that I'd need to complete all the research for all the tomes I had already selected, in order to be able to select another tome. But this is not the case (thankfully; I think that would have been boring).

Currently, ~23 turns into the game, and I just unlocked a tier II tome (Tome of Glades), but all I had was:

1. Tome of Roots (tier I) with 2/5 techs researched.
2. Tome of Beasts (tier I) with 4/5 techs researched.

So what exactly are the rules for being able to choose another tome to add to your list of research possibilities?

[CrUsHeR]

There's a button to show all tomes, then you can pick any unlocked tome on the left side.

[PatanWan]

Hey, can't check the game right now, but if I remember correctly, when offered a new tech or spell or whatever to research, there's a counter on the bottom left that says something like you need to research X more techs to unlock a new tome.

Then for your tier 2 tome you need to have two tier 1, for your first tier 3 two tier 2 etc. The first three tiers can be of any affinity, but tier 4 and 5 you need a certain amount of affinity to unlock, so if you're focused mainly on order, you will only have order tomes to choose from. Also I believe you can only choose one tier 5 tome, as opposed to tiers 1 to 4 where you can choose two.

Hope it helps! Cheers

EDIT: Also keep in mind there are specific techs depending on culture, and also general techs (like the magical crows for exploring), so maybe you also researched some of that and that's why you unlocked a third tome

[GrandMajora]

After every 4 research cycles, you unlock a new tome. To unlock the next tier, you need 2 tomes from the previous tier first. So to unlock Tier 2, you need to have 2 tomes from Tier 1 first. To unlock Tier 3, you need 2 tomes from Tier 2, and so on.

For Tier 1-3 tomes, you can obtain them whenever you want. Even skipping their 1st and 2nd tiers entirely and going straight for 3.

However, in order to obtain a Tier 4 tome, you need a minimum of 6 ranks in its respective affinity. While to obtain a Tier 5 tome, you need a minimum of 8 ranks.