The Animus books are by far the grindiest part of the old relic. Just keep at it, don't burn yourself out and maybe only task yourself with doing only 1 book a day?

When I finished my Animus phase it took me less than a day to get to the Zodiac phase. The rest of the relic past the books is a breeze to finish.

Tip: Sastasha/Tam Tara unsync are the fastest light you will get. If you run one and it doesn't have bonus, switch to the other.